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Laser - matter interactionsBoris Lukiyanchuk
Singapore, 26 November 2018
Lecture 6.
Laser - matter interactions
Nonresonant processes Resonant processes
Physical Processes
Laser Thermochemistry
Vapor PlasmaProcesses
Plasmonics Photonics
NonlinearOptics
Resonant Chemistry
Lecture 6. Resonant Laser Chemistry
Lecture 1 Lecture 3 Lecture 2Lecture 5
Lecture 4
“The School of Athens” a fresco of Raphael in
the Papal Palace of the Vatican.
Leonardo da Vinci
1446 – 1523
Michelangelo
1475 – 1564Raphael
1483 – 1520Niccolò Machiavelli
1469 – 1527Plato walks alongside Aristotle
Raphael was the main architect of the St. Peter Cathedral.
Aristotle
384–322 BC
Plato
423 – 347 BC
Socrates
470-399 BC
Observation, reason, and experiment make up what we
call the scientific method.
Richard Feynman
Aristotle wrote the book “Physics”, where he gave thedefinition of matter and discuss the possible reasons ofthe matter transformations.
Antoine Lavoisier
1743 – 1794
The Feynman Lectures on Physics
If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one
sentence passed on to the next generations of creatures, what statement would contain the
most information in the fewest words? I believe it is the atomic hypothesis (or the
atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles
that move around in perpetual motion, attracting each other when they are a little distance
apart, but repelling upon being squeezed into one another.
Mikhail Lomonosov
1711 – 1765Stanislao Cannizzaro
(1826 – 1910)
John Dalton
1766 – 1844
They proposed the concept that substances consist of atoms.
Henry Eyring
1901 – 1981Michael Polanyi
1891 – 1976
In 1935 Eyring, and Polanyi developed the "activated-complex theory“. The theoretical
assumption was that the transition state was crossed very rapidly, on the time scale that applies to
molecular vibrations. That it would ever be possible to perform experiments over such short
times was something no-one dreamed of.
Quantum theory has shown that the existence of chemical forces is a direct consequence of the
laws of quantum mechanics.
A chemical reaction is a process that leads
to the chemical transformation of one set
of chemical substances to another.
Chemical reactions are accompanied by a
lost or release of energy.
George Porter
1920 – 2002
1967
Manfred Eigen
1927 -Ronald Norrish
1897 – 1978
19671967
"for their studies of extremely fast chemical reactions, effected by
disturbing the equilibrium by means of very short pulses of energy"
Flash photolysis is a pump-probe laboratory
technique, in which a sample is firstly excited by a
strong pulse (called pump pulse) of light by a
short-pulse light source such as a flash lamp. This
first strong pulse starts a chemical reaction or
leads to an increased population for energy levels
other than the ground state within a sample of
atoms or molecules.
Temporal resolution of flash photolysis
was on the level 10−3𝑠..
Walter Kohn
"for his development of the
density-functional theory"
John A. Pople
"for his development of computational
methods in quantum chemistry."
1998
Ahmed Zewail (1946 – 2016)
1999
"for his studies of the transition states of chemical
reactions using femtosecond spectroscopy"
1992
Rudolph A. Marcus
1923 -
"for his contributions to the theory of electron
transfer reactions in chemical systems"
RRKM theory
The Rice–Ramsperger–Kassel-Marcus (RRKM)
theory is a theory of chemical reactivity. It took
the transition state theory into account.
Assume that the molecule consists of harmonic
oscillators, which are connected and can exchange
energy with each other.
Assume the possible excitation energy of the molecule
to be E, which enables the reaction to occur.
The rate of intra-molecular energy distribution is
much faster than that of reaction itself.
Vladilen Letokhov
1939 - 2009
more than 850 scientific articles and 14 monographs in the field of laser
physics, spectroscopy, chemistry, biomedicine and astrophysics related with lasers.
Laser trapping
Laser cooling
Laser chemistry
Optical frequency standards
1997
Steven Chu
1948
Cohen-Tannoudji
1933William Phillips
1948
1999Ahmed Zewail
1946 – 2016
Roy Glauber
2005Letokhov Chebotaev 1978
Arthur Ashkin2018
Science, 180, pp. 451 - 458(May 4, 1973)
The main processes of the selective laser photophysics and photochemistry are:
I. selective separation of substances at the atomic and molecular levels;
II. selective chemical reactions with atoms or molecules of the desired kind (for chemical
separation) or in the desired direction (photochemical synthesis);
III. selective detection of atoms, molecules, or molecular bonds.
Types and areas of application of processes In selective laser photophysics and photochemistry.V. S. Letokhov, Sov. Phys. Uspekhi 21, pp. 57-96 (1978)
ELEMENTARY SELECTIVE PHOTOPROCESSES
Properties of atoms and molecules altered by excitation with laser radiation: 1) increase of
reactivity; 2) reduction in ionization energy; 3) reduction in dissociation energy; 4)
predissociation; 5) isomerization; 6) change in trajectory of motion.
Main methods of selective interaction of laser radiation with atoms and molecules
Atoms Molecules
1. photochemical reaction; 2. ionization;
3. change in the velocity or deflection of
a trajectory of selectively excited atoms.
2+. Two other methods:
selective photodissociation of molecules
and photoisomerization.
a) selective two-step photoionization of atoms; b) selective two-step photodissociation of
molecules and comparison with photochemical processes.
Types of photoexcitation
a) one-step excitation of an
electronic or vibrational
state; b) two-step excitation
of an electronic state via an
intermediate vibrational or
electronic state; c)
multiphoton excitation by
infrared radiation.
Comparison of Different Photochemical Molecular Processes.
Photochemical separation of
mercury atoms, based on an
increase in the rate of reaction
of the excited mercury atoms
(A*) with oxygen (acceptor R).
W. Kuhn and H. Martin,
Naturwissenschaften 20, 772
(1932); Z. Phys. Chem. Abt. Β
21, 93 (1933).
However, the case of the
mercury atoms is exceptional
because of the existence of
metastable triplet states and
high-intensity mercury lamps.
PHOTOPHYSICAL ISOTOPE SEPARATION METHODS
a) two-step photoionization; b) three-step photoionization; c) two-step photoionization via an
autoionizing state; d) two-step selective excitation of a Rydberg state and its photoionization by IR
radiation; e) two-step selective excitation of a Rydberg state and its ionization by an electric field.
A common feature of all the selective ionization schemes is the following sequence of processes: 1)
selective excitation; 2) ionization of the excited atoms.
The first successful selective two-step ionization of atoms (of rubidium): JETP Lett. 13, 217 (1971)Separation of uranium isotopes: Livermore Laboratory: IEEE J. Quantum Electron. QE-10, 790 (1974).
Selective two-step (IR + UV) photodissociation
The two-step photodissociation of molecules is more complex than the two-stepphotoionization of atoms because of the following effects which influence the selectivity andrate of the process: l) the thermal nonselective excitation of vibrational levels; 2) thesmearing out of the edge of the electronic photoabsorption band of molecules; 3) thebottleneck effect due to the rotational structure of vibrational levels. The first two effectsrestrict the dissociation selectivity and the third sets an upper limit to the rate of absorptionof IR radiation by a molecule and, consequently, to the rate of the two-step photodissociationof molecules in a gas.
a) two-step IR + UV photodissociation; b) multistep selective excitation of high vibrational levels and theirphotodissociation by UV radiation; c) multiphoton selective excitation and dissociation by a single-frequency intense IR field; d) multiphoton selective excitation of vibrational levels by a resonant IR fieldand multiphoton dissociation of these levels by nonresonant intense IR radiation.
Multiphonon dissociation of molecules
It utilizes only high-power IR laser radiation for the direct excitation of very high vibrationallevels in the ground electronic state: isotopically selective dissociation of polyatomicmolecules (BCl3, SF6, OsO4 and others) by high-intensity CO2 laser pulses.
a) selective multistep excitation by triplevibrational-rotational resonance andsubsequent excitation of molecules in"vibrational quasicontinuum"; b) selectiveexcitation due to triple resonance followedby "leakage" to the vibrationalquasicontinuum.
Isotopic effect in the bands of nitromethane:
linear absorption spectrum at 20 Torr. CH315NO2
(solid) CH314NO2 (dashed).
The various transitions in themolecule's rotational quantumnumber J. R-branch correspondsto J = + 1, the P-branch to J = - 1 ,and the Q-branch to J = 0.
Dissociation of a diatomic molecule in a strong laser field: G. A.
Askaryan, Sov. Phys. JETP 19, 273 (1964); 21, 439 (1965); F. V.
Bunkin, R. V. Karapetyan, A. M. Prokhorov, Sov. Phys. JETP 20,
145 (1965).
Gurgen Askaryan
1928 – 1997Fedor Bunkin
1929-2016
Prokhorov 1916 - 2002
A. Prokhorov
1916 - 2002
PHOTOCHEMICAL ISOTOPE SEPARATION METHODS
1. Electronic photochemistry (subject of research before the appearance of lasers).2. Vibrational photochemistry (selective excitation of vibrational levels of molecules).
a) absorption of one photon in the fundamental band; b) absorption of one photon in thesecond overtone; c) two-step excitation in a two-frequency IR field; d) Raman excitation of avibration inactive in infrared absorption giving rise to two-frequency visible laser radiation;e) multiphoton excitation of high vibrational levels by single frequency intense IR radiation.
PREPARATION OF PURE SUBSTANCES
Selective dissociation of molecules
Purification of AsCl3 gas by selective dissociation of CCl4 and
C2H4Cl2 impurity molecules by CO2 laser radiation. The
absorption bands of the C2H4Cl2 and CCl4 impurity molecules
lie in the CO2 laser emission range, where there are no
absorption bands of the main substance AsCl3.
SELECTIVE LASER BIOCHEMISTRY
Selective excitation and breaking of hydrogen bonds in DNA
The double helix of DNA is formed by hydrogen bonds
between the guanine—cytosine and adenine— thymine
bases. Breaking of these hydrogen bonds should split the
double helix into two identical chains and result in
subsequent replication of DNA.
Excitation of levels by IR laser radiation to
stimulate proton tunneling.
SELECTIVE DETECTION OF NUCLEI,
ATOMS, AND MOLECULES
a) transition scheme; b) change in photoionization
cross section of selectively excited molecules.
An infrared mass spectrometer promises to be auniversal, highly selective, and very sensitivedetector of complex molecules, which may proveuseful in many scientific and technicalapplications. In fact, since the detection of excitedmolecules by photoionization is highly sensitive, itshould be possible to determine the IR spectra ofextremely small amounts of matter, much smallerthan those that can be tackled by the best existingclassical and laser infrared spectrometers.
SPATIAL LOCALIZATION OF MOLECULAR BONDS
A laser ion microscope for spatiallocalization of molecular bonds.
The function of the electric field is only to
transfer electrons or ions along radial
trajectories to the projector screen. The
selective photoionization of specific
molecular bonds in a macromolecule, which
is located on the tip of the projector, is
performed in accordance with the multistep
scheme using several picosecond laser
pulses with specially selected frequencies.
Vladimir Akulin
V. M. Akulin, N. V. Karlov, Boris S. Luk'yanchuk
Nonthermal Stochastic Behavior of Polyatomic
Molecules under the Action of Resonance
Laser Field Resulting from the Presence of
Special Domains in the Phase Space of
Vibrational VariablesBulletin of the Academy of Sciences of the U.S.S.R,
Physical series 47 (8), pp.1573-1577 (1983)
Vibrational motion of a highly excited molecule. Dynamics of excitation
of coupled anharmonic oscillators under the action of a resonant external
force. The calculation results show the absence of thermal energy
distribution over molecule degrees of freedom. The trajectory, starting from
a certain region of the phase space, continues to remain in this region for a
long time. Movement of the molecule is stochastic. The impact of quantum
fluctuations is especially important in areas of a “tangle type” on a phase
trajectory.
The acquired energy of the molecule vs time for different levels of fluctuations.
The projection of the phase trajectory on the plane {I,J).
Laser action selectivity and diffusion control
Pyotr Lebedev 1866-1912measure the pressure of lighton a solid body in 1899
Ashkin's greatest achievements
were to come in the study of
radiation pressure—the idea that
light and other forms of radiation
can exert a force on objects.
2018
Anatoly Shalagin
F. Gelmukhanov, A. ShalaginLight-induced diffusion of gases
JETP Lett 29, 711 (1979)
The traveling light wave produces
a macroscopic flux of absorbing
particles, if they are mixed with a
buffer gas. The flux is directed
either forward of propagating
wave or away from it.
P mv
F I
Because of the Doppler effect, the atoms whose velocities satisfied
the condition - mn = kv interact most effectively with thefield. If << kv Bennett peaks and dips. > kv sum ofequilibrium (Maxwellian) and antisymmetric parts. Jn and Jm fluxesbuck each other. If the gas of absorbing atoms is mixed with thebuffer gas, then the partial fluxes set in motion of absorbing gas as awhole (dimension of atom in the ground state and excited state aredifferent).
F - mn
Laser action selectivity and thermal diffusion with positive feedback
Carl Ludwig
1816-1895
Thermophoresis (also thermodiffusion, the Soret
effect, or the Ludwig–Soret effect) is a
phenomenon observed in mixtures of mobile
particles where the different particle types
exhibit different responses to the force of
a temperature gradient.Ludwig discovered
thermophoresis in
liquid in 1856
T1 T2
Charles Soret
1854 – 1904
Soret understood
thermodiffusion
in 1879
John Tyndall
1820 –1893
M. Faraday
Thermophoresis in gas mixtures
1870
Sydney Chapman
1888 – 1970Lord Rayleigh
1842–1919
1904
James Maxwell
1831–1879
Ludwig Boltzmann
1844 - 1906
The Dufour effect (found in 1872) is
the energy flux due to a
mass concentration gradient occurring
as a coupled effect of irreversible
processes. It is the reciprocal
phenomenon to the Soret effect.
Louis DuFour
1832–1892
Lars Onsager
1903-1976
1968
"for the discovery of the
reciprocal relations bearing his
name, which are fundamental
for the thermodynamics of
irreversible processes."
The diffusion flux I and the heat flux
are due to the presence of
concentration and temperature
gradients
i = - α grad μ - β grad T,
q = - δ grad μ - γ grad T + μ i
See L.L. Fluid Mechanics, § 59
𝝏𝒄
𝝏𝒕= 𝑫∆𝒄
𝝏𝑻
𝝏𝒕= 𝝌∆𝑻
𝒅𝒄
𝒅𝒙=
𝑫𝑻
𝑫
𝟏
𝑻
𝒅𝑻
𝒅𝒙=
𝑫𝑻
𝑫
𝒅
𝒅𝒙l𝑜𝑔 𝑇 , where
𝑫𝑻
𝑫= α c (1− c), α is thermodiffusion coefficient.
Let us consider concentrations of components within the mixture of two gases as c and 1-c. established
gradient of concentration is
α ≈𝒎𝟐 −𝒎𝟏
𝒎𝟐 +𝒎𝟏
𝒏 − 𝟓
𝒏 − 𝟏here n is an exponent in the asymptotic of the repulsive force
between molecules ∝ = Τ1 𝑟𝑛 .
𝑑𝑐
𝑑𝑥= α c (1− c)
𝑑
𝑑𝑥ln𝑇 , or
𝑑𝒄
c (1− c)= α 𝑑 ln𝑇
𝒄
1− c= 𝑨𝑻𝜶
Considering 𝑐 = 𝑐1 at 𝑇 = 𝑇1 and 𝑐 = 𝑐2 at 𝑇 = 𝑇2 we find
𝑐1
1−𝑐1/
𝑐2
1−𝑐2=
𝑇1
𝑇2
𝒂≈ 1 + 𝛼 log
𝑇1
𝑇2
G. Müller & G. Vasaru,
The Clusius-Dickel Thermal
Diffusion Column – 50
Years after its Invention,
Isotopenpraxis Isotopes in
Environmental and Health
Studies 24, pp. 455-464
(1988).
F. V. Bunkin, N. A. Kirichenko, B. S. Luk'yanchuk
Diffusion instability in a laser radiation field
Sov. J. Quantum Electron. 13, 1430 (1983)
T (t = 0) = 𝑇𝑤 ,𝑛 𝑡 = 0 = 𝑛0
Latest results
Thermophoresis at solids interfaces:
Schoen P. A. E. et al, Nanoparticle Traffic on Helical Tracks: Thermophoretic Mass Transportthrough Carbon Nanotubes, Nano Letters 6 (9), pp. 1910–1917 (2006) – theory.
Barreiro A. et al, Subnanometer motion of cargoes driven by thermal gradients along carbonnanotubes, Science 320, pp. 775–778 (2008) - experiment.
Negative thermophoresis in fluids:
Dwyer H. A., Thirteen‐Moment Theory of the Thermal Force on a Spherical Particle, Physics ofFluids 10, pp. 976–984 (1967) - theory.
Sone Yoshio, A Flow Induced by Thermal Stress in Rarefied Gas, Journal of the Physical
Society of Japan. 33, pp. 232–236 (1972).
Negative thermophoresis at solids interfaces
Leng Jiantao et al, Negative Thermophoresis in Concentric Carbon Nanotube Nanodevices, Nano Letters 16, pp. 6396–6402 (2016).
Literature
1. V. S. Letokhov,
Laser Control of Atoms and Molecules,
Oxford University Press, 2007
2. V. M. Akulin,
Dynamics of Complex Quantum Systems,
Oxford University Press, 2007
3. Rolf Haase,
Thermodynamics of Irreversible processes,
Dover, 1990