Generation of coherent terahertz radiation based on CO2 laser mixing and its
application to molecular spectroscopy of interstellar species
Fusakazu Matsushima
Department of Physics,University of Toyama, Japan
KAGRA face to face meeting,,Kashiwa, July 31, 2012
Univ. of Toyama and KAGRA Group Joint workshop
July 7, 2012 in Toyama
Many staffs in the faculties of science and engineering have much interest in KAGRA project.
Now organizing researcher groups in Toyama U.. Coming Soon !!
Microwave Physics Lab.
Control of motion of molecules using Microwave → ultracold molecule
→ fundamental physicselectric dipole moment of electrontime evolution of fundamental constants
Spectroscopy of interstellar molecules
Laser Physics Lab.
Atoms/molecules in liq. He
Generation / selection of cold molecules
Terahertz spectroscopy of molecules ←
in my talk
1. Importance of the precise measurements in the far-infrared (terahertz) region
2. TuFIR spectrometer (CO2 laser difference frequency) 2-1. Principle 2-2. Application to molecules
HeH+, OH-, H2D+, H2O (vibrational excited state)
Terahertz spectroscopy
Wide scan spectrograph. for: Biological substance Non-destructive inspection
High resolution spectroscopy
Guanine
frequency
Target of the high precision / high resolution spectroscopy of moledules in the THz region
Rotational spectra of light molecules2 or 3 atomic molecules including hydrogen
ex. water, H2D+
● astronomy, ● remote sensing of atmosphere ●"test stone" for newly proposed theories
Vib. Spectra of molecules with internal rotation ex. methanol
Spectra with large amplitude vibration, inversion ex. Chain molecule
Vib. Rot spectra of molecular clustersH2O, CO, N2 ...
● interface of gas phase and condenced phase
Terahertz spectroscopy
Herschel Satelite 3.5m telescope, 2008 launch, 57 - 670μm
ALMA (Atacama Large Millimeter/submillimeter Array) 30GHz to 950GHz operation about 50 years from 2012
SOFIA (Stratospheric Observatory for Infrared Astronomy) 2.5m telescope on air craft (B747) from 2007 8 hours per mission, 120 mission per year, operate 20 years colaboration of the US (80%) and Germany (20%) 1-600 μm, Hot Water, Carbon Chemistry
weedsCH3OH (CH3 internal rotation) Freq. Table up to 1THzHCOOCH3 (CH3 int. rot.) Table up to 1.67THz, need for precisionCH3OCH3 (two int. rot.) Table up to 2.17THz, need for precisionCH3CH2CN (heavy mol.) Table up to 3.39THz, need for precisionSO2 (heavy mol.)
flowersH2O, O2, CO, ionic species
Accuracy needed : better than 100kHz .Want for data of vib. excited state.
International projects are in progress !
2. TuFIR spectrometer (CO2 laser difference frequency)
2-1. Principle
2-2. Application to molecules (mainly molecular ions)HeH+, OH-, H2D+
H2O (vibrational excited state)
MIM diode as detector / mixer
Chain for the measurement of CO2 laser frequency
Standard:Cs atomic clock
MIMdiode
whisker
CO2 fluorescence cell
Laser frequency (cavity length)
4.3mfluorescence
1st derivative
Stabilization of the CO2 laser frequency
Accuracy of stabilization
Accuracy of one CO2 laser 25kHz
Accuracy of difference freq. 36 kHz
Fig.1 TuFIR 分光計frequency range: up to 6THz
precision of the source: about 30 kHz
power: several tens to several hundreds nW
F1
F2
Fmw
F
Molecules and ions measured with TuFIR spectrometer in Toyama
(1) neutral molecules , radicals LiH, KH, 18 OH, NH
H2O (including isotopes, vibrationally excited state)
(2) molecules with internal rotation
CH3OH
(3) cation protonated rare gas atoms (HeH+ , NeH+ , ArH+ , KrH+ , XeH+ , including their isotopic species)
H2D+
(4) anion OH- , OD-
HeH+ Rotational Transition
transition frequency obs-calc
4HeH+ J=10 2010183.873 (202) 0.108J=21 4008733.084 (194) -0.148
4HeD+ J=21 2434626.571 (143) 0.077 J=32 3641427.274 (384) -0.210
J=43 4835691.417 (166) 0.039
3HeH+ J=10 2139522.472 (300) -0.213J=21 4265839.060 (300) 0.330
3HeD+ J=21 2696099.975 (255) -0.021 J=32 4031223.001 (511) -0.650
HeH+
Dunham coefficient Ykl
EvJ = ΣYkl(v+1/2 )k[J(J+1)]l
( a set of coefficientsYkl for each isotope)
To calculate all the isotopes with a set of coefficients Ukl
Ykl = μ-(k/2+l)Ukl
Reduced mass μis not enough to fit all the isotopes.
Ykl = μ-(k/2+l)Ukl [1+meΔHekl/MHe + meΔH
kl/MH] Correction terms usingΔvalues are necessary.
Breakdown of Born-Oppenheimer approximation.
HeH+
Delta coefficients included for HeH+
(v+ 1/2)k[J(J+1)]l
l 0 1 2 3 4 k
0 U Δ He U U U Δ H Δ H
1 U Δ He U U U Δ H
2 U U U U
3 U
HeH+
J =3← 2
3363550.5413363550.541 frequency frequency (( MHzMHz ) ) 3363658.5413363658.541intensity(arb. units)
intensity(arb. units)
OH-
transition frequency (MHz) J=43 4478174.516 (387) J=32 3363607.066 (238) J=21 2244776.819 (240) J=10 1123100.985 (324)
OD-
Frequency(MHz)
Frequency(MHz)Frequency(MHz) Frequency(MHz)
Frequency(MHz)
J=2←1 J=3←2
J=5←4 J=6←5 J=8←7
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D2O/O2=54.5/5Pa,AC1.2kHz,1.1A,4.8kV,Scan6 回 ,エタノール冷却 2 ,℃ 湿度 60%,FIR200mV( 100nW)≒
ND3/O2=35/10Pa,AC1.2kHz,1.0A,5.6kV,Scan3 回 ,水冷 , 湿度 29%,FIR140mV( 70nW)≒
ND3/O2=35/10Pa,AC1.2kHz,1.0A,5.6kV,Scan3 回 ,水冷 , 湿度 26%,FIR160mV( 80nW)≒
D2O/O2=23.5/5Pa,AC1.2kHz,1.2A,4.5kV,Scan3 回 ,水冷(溜め置き) , 湿度 60%,FIR150mV( 75nW)≒
ND3/O2=35/10Pa,AC1.2kHz,1.0A,5.6kV,Scan3 回 ,水冷 , 湿度 24%,FIR40mV( 20nW)≒
Fit 1196791.042(0.486)MHz
Rotational spectra of water in the Sun spectra
1995 L. Wallace et al. “Water on the Sun”, Science, vol.268, pp.1155-1158, May 1995
Spectroscopy in the laboratory
Flame sample Emission from discharge cell
IR, FIR Fourier transform
H2O
Spectra near the Sun spot (L. Wallace 1995)
* lines of water(Even the rotationallines in the v=0 state,high J lines cannotbe calculated noridentified.)
H2O
Frequency (MHz)
423414 line in the (1,1,0) vibrational state
Energy of the 414 level: 5457.4 cm-1
H2O