PS451 Final Year Project Literature Survey:

The Processes and Applications of Spectroscopy:

Characterizing Plasma Emissions

Daniel Hurley

Student ID: 12377626

Class: PHA4

Supervisor: Dr. Bert Ellingboe

2015

Abstract

This literature survey focuses on the science of spectroscopy and

how it is applied to plasmas. Spectroscopy is used to determine the

characteristics of plasmas, such as, the electron temperature and den-

sities. If enough information is gathered from a plasma, the emit-

ting species can be identified. Plasma is the most abundant state of

matter in the universe, from the Aurora Borealis to the ionized hy-

drogen clouds in space. There are several types of plasmas and some

require their own diagnostic method. By investigating the emissions

from plasmas, collisional radiative models can be used to determine

these characteristics. In this literature survey, I will mention several

experiments that contributed to the growing number of methods to

analyse plasmas, and the assumptions these methods used. I explain

the basic instrumentation and set up of a typical spectroscopic exper-

iment. There have been a number of advances in plasma spectroscopy

and technology, and plasma spectroscopy has industry applications in

areas such as medicine, food analysis and many other disciplines.

1

Contents

1 Introduction 3

2 Plasma Spectroscopy 4

2.1 The Basic Science Behind Spectroscopy . . . . . . . . . . . . . . . . 4

2.2 Plasma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 Instruments and Set-up . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.4 Identifying Species . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3 Low Temperature Plasma Emissions 11

3.1 Population, Electron Density and Temperature . . . . . . . . . . . . 11

3.2 Measuring Line Width and Profile . . . . . . . . . . . . . . . . . . . 14

3.3 Collisional-Radiative Models . . . . . . . . . . . . . . . . . . . . . . 16

3.4 Assumptions in CR Models and Theory . . . . . . . . . . . . . . . . 17

4 Applications and Advances in Plasma Research 19

5 Conclusions 21

6 Appendices and Acknowledgements 22

2

1 Introduction

Newton started the science of spectroscopy when he studied the colours of the

rainbow, in the 1600s. Newton saw the relationship between wavelength and spec-

tral lines. Since then, spectroscopy has become a fundamental branch of science

that describes the interactions between matter and electromagnetic radiation. The

spectrometry work over the last few hundred years contributed to the formation

of what is known today as quantum mechanics. Atomic Spectroscopy is still stud-

ied today because it is useful when trying to acquire the energy level structure of

complicated atoms.[1] Spectroscopy has a wide range of applications in the world,

and in space, today. Spectroscopy is used to study the electromagnetic radiation

that comes from stars and other bodies in the solar system and beyond. Using

spectrometry techniques, the type of radiative energy, the type of material, and

the type of interaction between the energy and the material can be identified e.g.

emission and absorption lines. Plasmas were originally studied because they were

a source of radiation. They have been studied for the spectrochemical analysis

and atomic structure of the plasmas. Plasma spectroscopy studies the dynamic

characteristics of a plasmas radiation i.e. the atoms and ions releasing radiation.[2]

Plasma can be characterized with the help of collisional radiative models. These

models are used to identify characteristics of plasmas such as electron density and

temperature. But, the correct conditions for practical spectrometry must be cho-

sen. The data gathered can be affected by processes such as line broadening and

temperature. Depending on what region of the electromagnetic spectrum is being

studied, limitations arise.[3]

3

2 Plasma Spectroscopy

2.1 The Basic Science Behind Spectroscopy

Spectroscopy is the study of the interactions between matter and electromagnetic

radiation. By observing the emission, absorption or scattering of electromagnetic

waves by matter, the physical processes behind these interactions are be identified.

This provides insight into the properties of atoms and particles. [4][5] A simple

spectroscopy set-up would consist of a sample, a source of light, a monochromator

and a detector. The light beam from the light source passes through the sample.

The light passed through the sample is split by the monochromator. The light

from the monochromator is detected by the detector. The intensity of the light

vs the frequency of the light is recorded. The three focus areas of spectroscopy

are emission, absorption and Raman scattering. Emission spectroscopy focuses on

the transitions from high energy levels to low energy levels. Absorption focuses

on transitions from low energy levels to higher energy levels. Raman spectroscopy

focuses on the scattering of light due to vibrations. The difference between emis-

sion and absorption is illustrated in Figure 1.[5] The relationship between energy

Figure 1: Emission and Absorption Spectroscopy[6]

4

and frequency of a charged atomic oscillator is described by the Planck-Einstein

relation:

E = hv =hc

λ= hc

−v (1)

Where E is the energy, h is Planck’s constant, λ is the wavelength,−v is the

wave number, and v is frequency. This relationship can be used to determine

the energy transition between levels by observing the wavelength of the emitted

photon in emission spectroscopy. In absorption spectroscopy, the wavelength of

the light before and after entering a sample can be compared, and the change in

energy for that photon can be quantized.[2]

Ei = hvi and Ej = hvj (2)

The allowed transitions between energy levels can be mapped for a chemical

species. In hydrogen, each energy level is defined by:

En = −E0

n2(3)

Where En the electron energy at level n is, E0 is 13.6 eV for hydrogen, and

n is energy level. The allowed transitions between these levels are defined by the

hydrogen spectral series i.e. Lyman, Balmer, Paschen etc. The amount of energy

required to transition between one energy level to another is defined by:

∆E = E0(1

m2− 1

n2) (4)

Where m is the lower energy level and n is the higher energy level. By observing

the energy of the emitted photon, the spectral lines observed can be classified. [5]

The transitions between energy levels are illustrated in Figure 2. This shows the

spectral line series for Lyman, Balmer and Paschen.

5

Figure 2: Spectral Line Series

The Maxwell-Boltzmann distribution describes the probability of what speed

a particle has. This depends on the temperature and mass of the particle.

Nj

Ni

= exp(−∆E

kT) (5)

Where Nj is the higher state population, Ni is the lower state population, k is the

Boltzmann Constant, T is the temperature, and E is the energy.[5]

6

2.2 Plasma

Plasma is the fourth state of matter i.e. ionized gas. Plasma can be partially

or completely ionized. Plasma is an electrically neutral medium of positive and

negative particles. These particles are unbound. Charges create electrical currents

and magnetic fields. These charges are affected by one another’s fields.[7]

There are three main components that define plasma:

• The particle density n (Particles/cm)• The temperature T (eV)• The magnetic field B (T)

There are many types of plasma. Three general examples of the types of

Plasmas found on and off earth are listed below. [4]

Non-fusion terrestrial plasmas:

• Neon Signs, Fluorescent Lamps, Arcs• Typical Density of about 1014 - 1022 m−3 and Temperature of a few eV• Very common plasmas on earth• Inexpensive production

Fusion terrestrial plasmas:

• Fully ionized Hydrogen and Deuterium• Typical Density of about 1020 m−3 and temperatures in multiples of 104 eV• Very expensive to produce• Quite rare on earth

Space plasmas:

• Density varies from 106 - 1020 m−3 depending on location• Temperatures of up to 100 eV• Fully ionized (usually)

Three important sources of photons are from bremsstrahlung, radiative recom-

bination and bound-bound transitions. [8] Partially ionized gas is of particular

interest for my final year project. Low temperature plasmas typically have cold

ions and neutrals, and hot electrons. Each species is characterized by its own

temperature.

7

2.3 Instruments and Set-up

In plasma spectrometry, typically, Czerny-Turner monochromators are used to

split incoming electromagnetic radiation into separate components. The Czerny-

Turner configuration can be seen Figure 3. The choice of grating and focal length

for these monochromators are important because they determine the resolution

that can be worked with. The blaze angle of a grating determines the sensitivity

of the grating. A CCD detector is at the exit of the monochromator. These are

able to record specific wavelength ranges.[3] The basic process of a spectroscopic

experiment using plasma: Electromagnetic light is emitted from the plasma. The

light enters the entrance slit of a monochromator. The light is split by the diffrac-

tion grating in the monochromator. The desired component of light exits through

the exit slit and is detected by a CCD camera. The species is then identified using

various spectroscopic techniques.

Figure 3: Czerny-Turner Spectrometer Configuration[9]

There are limitations in plasma spectroscopy. So, choosing the correct condi-

tions to work in is important. The temperature and the region of the EM spectrum

can have an effect on the results of a spectroscopic experiment. The 200 nm to

1000 nm range encapsulates the visible spectrum, along with part of the UV and IR

8

Figure 4: Spectra for H2 and D2 indicating P, Q and R branches[10]

spectra. Working outside of the 200 nm to 1000 nm range will cause issues to arise

as mentioned in [3]. When working in a range less than 200 nm, quartz glass and

Oxygen cause issues. Quarts glass becomes less transparent, and Oxygen absorbs

light. This means a vacuum path must be set up to prevent Oxygen absorbing the

light. When working in a range above 1000 nm, noise becomes an issue. Thermal

background noise must be compensated for using detection equipment. This raises

experimental costs. Emission and absorption spectroscopy require different meth-

ods. Emission spectroscopy is considered a straight-forward process and ideal for

learning the properties of plasmas. Absorptions spectroscopy on the other hand,

is more difficult to conduct. The hydrogen and deuterium spectra for this region

can be seen in Figure 4.[3]

2.4 Identifying Species

Spectroscopy is very important for identifying the species within a plasma. This

can be achieved by analysing the emission intensity. Particles emit radiation.

9

The a product of the rate that the upper state is populated, and the electron

collisions, and what fraction of the upper state decays through the pathway, gives

the emission intensity. Once the atomic data for the transitions and the electron

temperature is known, the relative intensities for all the emission lines can be

calculated. For excited atomic hydrogen, the population is coupled to H and H+

particles with their own densities. This relationship is given as:

nH(p) = nHneRH(p) + nH+neRH+(p) (6)

Where RH(p) and RH+(p) are the population coefficients which are calculated

using a collisional radiative model. Line identification can be difficult as the

higher order lines may be near the line that is to be identified. This is why it

highly important to use filters. These filters block out the unwanted lines that may

interfere with the line being analysed. Choosing a filter to work with depends on

the region of the EM spectrum being analysed. Filters can be expensive depending

on which region or how close the lines are together. The position of the line is

the identifier in spectroscopy. Using the position, the lines can be identified using

databases (IAEA and NIST are recommended[8]) that contain accurate values for

these lines and can therefore be cross-referenced with the data obtained.[3]

Figure 5: Gas temperature obtained from the fit of the computer simulation to

the measurement of a vibrational band of N2 [3]

10

3 Low Temperature Plasma Emissions

3.1 Population, Electron Density and Temperature

In low temperature plasmas, Telectron � Tion ≥ Tneutral with Te = 8eV and typ-

ically have a small percentage of ionization. Nearly all the molecules are in the

vibrational ground state and deviations from the 2000 Kelvin distribution do not

change the upper Fulcher state population.

dnupperdt

= (nlower)(ne)

∫ ∞0

σ(v)F (v)dv (7)

Where σ(v) is the velocity dependent cross section and F (v) is the EEDF. Elec-

trons have sufficient energy to cause energy state transitions in the gas. This

depends on the electron temperature and the change in energy for that transition,

and the cross section. The cross section for the l→p excitation is given by:

σl,p = 2/(XUl,p)[1+sl,pexp(−rl,pUl,p)]×[Al,p[lnUl,p+1/(2Ul,p)]+(Bl,p−Al,pln2/x)(1−1/Ul,p)]πa20

(8)

Where Ul,p is the electron energy, X is the energy difference of the levels, Al,p and

Bl,p are the parameters of the Born approximation, and a0 is the Bohr radius.

These parameters are adjustable for different scenarios. Different excitation chan-

nels happen at different rates. To understand plasma reactions, the vibrational

excitation of molecular hydrogen in the ground state is of particular interest. Vi-

brations are associated with the stretching and bending of molecules. Identifying

the species becomes easier when the vibrational level is known. The vibrational

population in ground state hydrogen molecules is an important component for the

formation of negative ions in plasma. In an experiment to determine the vibra-

tional population in the hydrogen ground state, Fantz says “Vibrationally exited

molecules lead to the formation of negative ions and to an increase in ionization and

dissociation rate coefficients”. It was also found that there is no collisional swap-

ping in the higher states.[10] The vibrational population is given by the Boltzmann

distribution. See equation 5. Raman scattering techniques were used to measure

the vibrational population of radio frequency plasma in an experiment by V. A.

Shakhatov.[11] A typical population density for low temperature plasma would be

ne ≈ 1017m−3. The typical electron temperature for plasma would be Te ≈ 5eV .

11

By using different diagnostic gases, the electron density and electron temperature

can be determined from the line ratios from emission lines and the electron den-

sity. Using collisional radiative models, ratios of effective emission rate coefficients

can be identified. Emission rate coefficients are dependent on electron density and

electron temperature. In low temperature plasma, the electron temperature is

highly important for analysing these line emissions. Figure 6 shows the ratio of

emission coefficients for the helium line at 728 nm to Argon at 750 nm.[3]

The calculation of the negative ion population density can be simplified to this

equation:

nH− =Hy

neC1(

Hα

Hβ

1

C2

− 1). (9)

This can be used to monitor the negative ion densities.

The processes of plasmas can be seen in the excitation pathways of hydrogen.

There are four pathways for molecular hydrogen.

Firstly, the direct ionization from electron impact is given by:

H2(X1Σ+

g ) + e→ H+2 (X2Σ+

g ) + e+ e (10)

The second excitation pathway starts from the ground state and produces an

exited molecule:

H2(X1Σ+

g ) + e→ H∗2 + e (11)

H∗2 + e→→ H∗∗2 + e

H∗∗2 + e→ H+2 (X2Σ+

g ) + e+ e

Third is the dissociative ionization from an unstable molecular hydrogen ion

is given by:

H2(X1Σ+

g ) + e→ H(1s) +H+ + e+ e (12)

Forth is the ionization from excited hydrogen atoms from dissociative excita-

tion of molecular hydrogen is given by:

H2(X1Σ+

g ) + e→ H(1s) +H∗ + e (13)

H∗ + e→→ H∗∗ + e

H∗∗ + e→ H+ + e+ e

12

If the atomic data is known for a transition, and the electron temperature is

known, then it is possible to calculate the relative intensities of the emission lines

of the plasma. [12] [13]

Figure 6: Ratio of emission rate coefficients forHe728Ar750

[3]

13

3.2 Measuring Line Width and Profile

The spectral lines detected from plasmas can be broadened; this means the lines

may have shifted positions, and are not as sharp as they could be. A common

example of this is Doppler broadening. Doppler broadening occurs in the visible

to UV region. Atoms travelling towards the detector will have different transition

frequencies from those at rest. In terms of wavelength, width of the spectral line

at the half height of the profile, called the Full-Width Half-Maximum (FWHM),

is expressed as:

2∆λ 21

= 2√

ln 2λ0

( 2kTiMic2

) 12

(14)

Where λ0 is the central wavelength, Ti is the ion temperature, λ 21

is the Doppler

half width in terms of wavelength, c is the speed of light, and k is the Boltzmann

constant.[2] The line width and FWHM can be seen in Figure 7. A common

type of broadening that occurs is The Doppler Effect. This causes a shift in the

central wavelength. Other types of broadening can occur due to quasi-static and

temporal changes in the atomic states of the ions that are emitting energy. Line

width is a regular concern in experimental plasma research. The profile shape of

spectral lines depends on the density of charged particles. Stark Line broadening

complicated the interpretation of an experiment to investigate the relationship

between plasma and liquids in an experiment by P. Bruggeman.[14] The Spectral

line intensity is given by:

Iij = Nj · Aij · Eij (15)

Where Iij is line intensity, Nj is the upper state density, Aij is Einstein Coefficient,

Eij is the photon energy.[8]

14

Figure 7: Line Width[15]

15

3.3 Collisional-Radiative Models

Photons carry information about plasmas. Using theoretical plasma spectroscopy

techniques, the thermodynamic properties of plasma and the behaviour of plasma

can be modelled. Different models are required for different plasmas. For collisional-

radiative plasmas, the population distribution is determined using rate equations,

taking into account the collisional and radiative processes. Other effects such

as radiation transport and density effects must be included in a model.[16] The

master equations for the construction of a Collisional-Radiative Model are: [17]

dn+

dt=dnedt

= −ne(ΣiRi + neΣiQi)n+ + neΣiSei ni (16)

dnidt

= neΣi 6=jnjKeji−nine(Sei +Σj 6=iK

eij)+n+n

2eQ

ei−niΣj<iAij+Σj>iAijnj+n+neRi

(17)

Collisional-Radiative Models are coded versions of the radiating properties of

ions and atoms within plasmas, constructed using the above master equations 16

and 17. They show the relationship between the ground state population and the

particle density.[18] “Collisional-radiative models describe the intermediate state

which exists before full thermal equilibrium is reached, but where the electron den-

sity is sufficiently high for electron collisions to compete with radiation in altering

the occupancy of excited atomic and ionic states”.[19] Collisional Radiative mod-

els were made for atomic hydrogen in high velocity plasma flow in an experiment

by S. Sun and H. Wang. They investigated the kinetic processes of a hydrogen

plasma arc-jet thruster. They discovered that a collisional radiative model worked

for different regions of the arc-jet. They concluded that the population densi-

ties of the excited states of hydrogen followed the Boltzmann distribution. In

the lower states, however, the population density deviated from the Boltzmann

distribution.[20]

16

3.4 Assumptions in CR Models and Theory

Plasma spectrometry experiments cannot be conducted without the use of certain

assumptions. The Maxwell distribution is used to describe the electron impact

process in low temperature plasmas, even though it is not entirely justified. For

the rate coefficient, there is a steep dependence on electron temperature at low

temperatures and the quality of the cross section. An experimental error of a

factor of 2 must be applied in the case of low temperature plasma diagnostics as

seen in figure 6.[3]

The rate coefficient is described by: [3]

Xexc(Te) =

∫ ∞Ethr

σ(E)(2

me

)12

√Ef(E)dE (18)

In an experiment, by U. Fantz, and B. Heger, to show the spectroscopic di-

agnostics of the vibrational populations of the electron ground state of H2, as-

sumptions were used for the diagnostics method. The Franck-Condon principle

for electron impact excitation was assumed to be valid. [10] The Franck-Condon

principle states that “the intensity of a vibronic transition is proportional to the

square of the overlap integral between the vibrational wave functions of the two

states that are involved in the transition”. This means that one energy level may

not be able to get to certain excited states as the probability of finding the popu-

lation at the same location in the next state is very low. Using this assumption,

it was possible to characterize the population using the vibrational temperature.

These assumptions were justified by the use of a collisional radiative model, which

qualitatively tested it’s validity. The Franck-Condon assumption allows for the

identification of H+ particles if there is an ion temperature higher than the gas

temperature and lower than the Franck-Condon energy. [21]

According to H. K. Chung, assumptions must be made when creating colli-

sional radiative models. For example, “the ionization potential depression model

of Stewart and Pyatt is used to suppress bound states due to continuum lower-

ing”. In coronal plasmas, at low density, the excited state population density is

so low that they are assumed to be populated from the ground state by collisional

excitation and depopulation by spontaneous emission. So, in this case, the excited

population is proportional to the stark broadening. [16]

17

In the experiment previously mentioned by S. Sun and H. Wang, it was assumed

that the plasma they investigated was electrically neutral, optically thin, and

that the energy distribution was Maxwellian. It was also assumed that electron

to atom collision frequencies dominates the kinetics, so ions to atom collisions

were neglected. This allowed the calculation of the cross-sections for super-elastic

collisions and three-body recombinations using the detailed balance principle. In

order to analyse the results, it was assumed that the initial distribution of the

excited states followed the Boltzmann distribution.[20]

18

4 Applications and Advances in Plasma Research

Innovations have been made in the medical applications of plasmas. Plasmas can

be used in anticancer therapy that does not have an affect on the areas near the

tissue of interest. This method is based on the dielectric barrier discharge principle.

This device is made of two planar electrodes separated by a gap. However, the

human body can act as one of these electrodes, meaning non thermal atmospheric

plasma may be used as in anticancer therapy. This has been successfully tested on

mice with a resulting 60 percent increase in lifespan due to tumour size reduction.

The experiment did not exceed 5 days however. Considering the difference in size

between mice and humans, longer duration and exposure to plasma therapy may

be required, which has not extensively been investigated in terms of safety in this

experiment.[22]

Plasmas are used to produce negative ion sources. A new, non-invasive, method

to diagnose plasmas and determine the negative ion densities was created by U.

Fantz and D Wunderlich. Using optical emission spectroscopy, this method anal-

yses the Balmer line ratio of Hα and Hβ and discovered that there was a linear

correlation between the line ratio and the negative ion density of the source. This

method was applied to Radio Frequency plasmas in the IPP. Although, there were

uncertainties, due to the use of a collisional radiative model, in this experiment

resulting a 20 percent error bar. The reliability of a collisional-radiative model

depends on the input data quality. This uncertainty is due to the assumption that

the error in the negative ion density is less than 40 percent. [23]

Plasma research is a continually growing field of research. A popular topic at

the moment is in relation to plasmas in contact with liquids. In an experimental

evaluation of this interaction, it was discovered that the emission spectrum is de-

termined mainly by the production processes and kinetics of the emitting species,

after investigating a 600 Nano second pulsed discharge in Oxygen bubbles using

temporal optical emission spectroscopy.[14]

Plasma spectroscopy is also used to identify metals in wine and arsenic in foods.

Wine is a complex organic compound, making it difficult to analyse. Spectroscopy

can be applied to separate the components, making them easier to identify. The

spectroscopy techniques used are preferable to any other as they are not prone to

19

interference from organic compounds. This is because there is a high temperature

involved in the atomization steps. Spectroscopy is a fast and highly accurate

technique for determining the imperfections in wines.[24]

Plasma spectroscopy is regularly used in astronomy to study the constituents

of stellar and interstellar material. Plasma is the most abundant state of matter in

the universe, making it an area of high interest for spectroscopy. The constituents

of space plasmas can be derived from lines observed by telescopes, such as the

XMM-Newton. Advances have been made in plasma diagnostics of coronae using

spectroscopy. Obtaining the temperature and densities of plasmas in the past

relied upon the use of atomic databases, which contain information based on the

plasma structure, such as line emissivity. The XMM-Newton telescope is equipped

with gratings that provide higher resolution than previous missions. Gratings on

the newer telescopes can resolve in the Angstrom range, making it possible to

obtain larger amounts of information from just a few lines. Now, it is possible to

determine the temperature and densities of stellar plasmas just by observing the

lines. The new technology reduces the need for global models.[25] Ionized hydrogen

clouds can be examined using plasma spectrometry. By examining the emissions

of a cloud, the components of that plasma can be identified and analysed. Using

collisional radiative models, as discussed in an earlier section, can help to the

identify the stellar and interstellar material that makes up any star or cloud.[26]

20

5 Conclusions

Spectroscopy is an exciting field of scientific research. Ever since Newton observed

the rainbow, new techniques and methods have been discovered on how to analyse

the spectra of plasmas. Spectroscopy is a vital science to industry and plasma

spectroscopy is a key branch in this industry. Space science benefits greatly from

the discoveries made in optical emission spectroscopy. Now it is easier to gather

information about stellar and interstellar plasmas due to advances in technology

i.e. high resolution gratings and collisional-radiative models and anticancer ther-

apy. As the mysteries of plasmas are uncovered, they will undoubtedly benefit our

knowledge of atomic structures and interactions. With spectroscopy, the charac-

teristics of plasmas such as the electron density and electron temperatures can

be identified. Collisional-radiative models can be used to compare the behaviours

of plasmas. Choosing the appropriate parameters, such as temperature and the

region of the spectrum, to work with is important for spectroscopic experiments.

Plasma spectroscopy is a relatively new field of research, so numerous discoveries

can be expected in the near future. The information I have gathered for this sur-

vey will aid me in my final year project as it has provided a basis for my knowledge

of plasmas and spectroscopy.

21

6 Appendices and Acknowledgements

References

[1] R. Herrmann and C. Onkelinx, “Quantities and units in clinical

chemistry: Nebulizer and flame properties in flame emission and absorption

spectrometry,” Pure and Applied Chemistry, vol. 58, no. 12, pp. 1737–1742,

1986. [Online]. Available: http://www.degruyter.com/view/j/pac.1986.58.

issue-12/pac198658121737/pac198658121737.xml

[2] T. Fujimoto, Plasma Spectroscopy. Oxford Science Publications, 2004. [On-

line]. Available: http://www.oxfordscholarship.com/view/10.1093/acprof:

oso/9780198530282.001.0001/acprof-9780198530282

[3] U. Fantz, “Basics of plasma spectroscopy,” Plasma Sources Science and

Technology, vol. 15, no. 4, pp. S137–S147, 2006. [Online]. Available:

http://iopscience.iop.org/article/10.1088/0963-0252/15/4/S01/pdf

[4] P. J. Cargill, “Fundamentals of Plasma Physics,” Plasma Physics

and Controlled Fusion, vol. 49, no. 2, 2007. [Online]. Available:

http://iopscience.iop.org/article/10.1088/0741-3335/49/2/B01/pdf

[5] A. Ellingboe, “Applied Spectroscopy Course Material,” 2015.

[6] Wikiversity.com, “Emission and Absorption Illustration,” 2015. [On-

line]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f2/

Absorption or emission spectroscopy.png

[7] P. A. Sturrock, Plasma Physics: An Introduction to the Theory of Astro-

physical, Geophysical & Laboratory Plasmas. Cambridge University Press,

1994.

[8] Y. Ralchenko, “Introduction to Qualitative Plasma Spectroscopy Lecture

Slides,” 2012. [Online]. Available: https://www-amdis.iaea.org/Workshops/

ICTP2012/Yuri.Ralchenko-Lectures-ICTP-2012-01.pdf

22

[9] Stackexchange.com, “Czerny-Turner Configuration Illustration,” 2015.

[Online]. Available: http://physics.stackexchange.com/questions/179547/

what-are-the-purposes-of-slits-inside-a-spectrometer-czerny-turner

[10] U. Fantz and B. Heger, “Spectroscopic diagnostics of the vibrational

population in the ground state of and molecules,” Plasma Physics

and Controlled Fusion, vol. 40, no. 12, pp. 2023–2032, 1998. [Online].

Available: http://stacks.iop.org/0741-3335/40/i=12/a=003?key=crossref.

cf9e94355b577cf8626445ce8d59dc3d

[11] V. a. Shakhatov, O. De Pascale, M. Capitelli, K. Hassouni, G. Lombardi,

and A. Gicquel, “Measurement of vibrational, gas, and rotational

temperatures of H2 in radio frequency inductive discharge plasma by

multiplex coherent anti-Stokes Raman scattering spectroscopy technique,”

Physics of Plasmas, vol. 12, no. 2, p. 023504, 2005. [Online]. Available:

http://scitation.aip.org/content/aip/journal/pop/12/2/10.1063/1.1829065

[12] L. Dosoudilov, “Collisional Radiative Model Lecture Slides,” 2015. [Online].

Available: http://physics.muni.cz/∼dorian/Dosoudilova.pdf

[13] K. Sawada, K. Eriguchi, and T. Fujimoto, “Hydrogen-atom spectroscopy

of the ionizing plasma containing molecular hydrogen: Line intensities and

ionization rate,” Journal of Applied Physics, vol. 73, no. 12, p. 8122,

1993. [Online]. Available: http://link.aip.org/link/JAPIAU/v73/i12/p8122/

s1&Agg=doi

[14] P. Bruggeman, T. Verreycken, M. A. Gonzalez, J. L. Walsh, M. G. Kong,

C. Leys, and D. C. Schram, “Optical emission spectroscopy as a diagnostic

for plasmas in liquids: opportunities and pitfalls,” Journal of Physics D:

Applied Physics, vol. 43, no. 12, p. 124005, 2010. [Online]. Available:

http://iopscience.iop.org/article/10.1088/0022-3727/43/12/124005/meta

[15] Bdnyc.com, “Line Width Illustration,” 2015. [Online]. Available: http:

//www.svi.nl/wikiimg/FWHM.png

[16] H. K. Chung, “Atomic processes modeling in plasmas modeling

spectroscopic observables from plasmas,” no. January, 2012. [On-

23

line]. Available: https://www-amdis.iaea.org/Workshops/ICTP2012/Hyun.

Kyung.Chung-Lecture1-ICTP-2012-01-23.pdf

[17] G. Colonna, L. D. Pietanza, and M. Capitelli, “On the Coupling of

Collisional Radiative Models and Boltzmann Equation for Atomic Transient

Hydrogen Plasmas,” pp. 222–229, 2001. [Online]. Available: http://oai.dtic.

mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA400895

[18] H. Summers, The ADAS User Manual, version 2.6, 2004. [Online]. Available:

http://www.adas.ac.uk

[19] P. T. Greenland, “Collisional-radiative models and molecular spectroscopy,”

Contributions To Plasma Physics, vol. 42, no. 6-7, pp. 608–615, 2002.

[Online]. Available: http://discovery.ucl.ac.uk/1307163/

[20] S.-r. Sun and H.-x. Wang, “Collisional-radiative model of atomic hydrogen in

high velocity plasma flow,” no. August, pp. 7–10, 2013. [Online]. Available:

http://www.ispc-conference.org/ispcproc/ispc21/ID190.pdf

[21] V. Gold, “International Union of Pure and Applied Chemistry Compendium

of Chemical Terminology,” Iupac, p. 1670, 2014. [Online]. Available:

http://goldbook.iupac.org/PDF/goldbook.pdf

[22] M. Vandamme, E. Robert, S. Dozias, J. Sobilo, S. Lerondel, A. Le

Pape, and J.-M. Pouvesle, “Response of Human Glioma U87 Xenografted

on Mice to Non Thermal Plasma Treatment,” Plasma Medicine, vol. 1,

no. 1, pp. 27–43, 2011. [Online]. Available: https://hal.archives-ouvertes.fr/

hal-00683299/document

[23] U. Fantz and D. Wunderlich, “A novel diagnostic technique for H- (D-

) densities in negative hydrogen ion sources,” New Journal of Physics,

vol. 8, no. 12, pp. 301–301, 2006. [Online]. Available: http://stacks.iop.org/

1367-2630/8/i=12/a=301?key=crossref.0f040596b412cad5387b13e4dcbc7d85

[24] M. Aceto, O. Abollino, M. C. Bruzzoniti, E. Mentasti, C. Sarzanini, and

M. Malandrino, “Determination of metals in wine with atomic spectroscopy

(flame-AAS, GF-AAS and ICP-AES); a review,” Food Additives and

24

Contaminants, vol. 19, no. 2, pp. 126–133, 2002. [Online]. Available:

http://www.tandfonline.com/doi/abs/10.1080/02652030110071336

[25] J.-U. Ness, “Advances of plasma diagnostics with high-resolution

spectroscopy of stellar coronae,” Advances in Space Research,

vol. 38, no. 7, pp. 1494–1500, 2006. [Online]. Available:

http://linkinghub.elsevier.com/retrieve/pii/S0273117705000384

[26] H. R. Griem, Principle of Plasma Spectroscopy, 1964. [Online].

Available: http://capitadiscovery.co.uk/dcu/items/96096?query=Principle+

of+Plasma+Spectroscopy&resultsUri=items?query=Principle+of+Plasma+

Spectroscopy

25