K. Iwakuni, H. Sera, M. Abe, and H. Sasada Department of Physics, faculty of Science and Technology,...

Sub-Doppler Resolution Spectroscopy of the Fundamental Vibration Band of

HCl with a Comb-Referenced

Spectrometer

K. Iwakuni, H. Sera, M. Abe, and H. SasadaDepartment of Physics, faculty of Science and Technology,

Keio University, Japan

170th. International Symposium on Molecular Spectroscopy

June 23, 2015 　 The University of Illinois

TF02

Outline1. Comb-referenced DFG spectrometer2. Observed spectra and analysis3. Assignment and determination of molecular constants

2

ν

frep

ECLD

Nd:YAG laser1.06 μm

1.55 μmPPLN

3.4 μm

ECAC InSbdetector

Comb-referenced DFG spectrometer

OFC

TAI synthesizer

Rb clock

Pump

Signal

Idler

The method of absolute frequency measurement

of the DFG light

4

ν

signal pump

fbeat2 fbeat1

νn1 = fceo + n1 frep νn2 = fceo + n2 frep

frep = 67 MHz・・・

0 Hz

fceo

νidler

• Absolute frequency• Narrow linewidth (250 kHz → 25 kHz) • Repeatability

sweep

High resolutionHigh accuracy

High sensitivity

νDFG = (n1‐n2) frep + ( fbeat1– fbeat2 )

Rb clock

1.55 μm

Comb-referenced +Wavelength-modulation DFG spectrometer

ν

frep

ECLD

Nd:YAG laser1.06 μm

PPLN

3.4 μm

ECAC InSbdetector

synthesizer

absolute frequency

signa

l

lock in amp.

modulation3 kHz

demodulation3 kHz

21.4 MHz

Rb clock

Sub-Doppler resolution spectrum of H35Cl R(0)

the fundamental vibration band

v = 1, J’ = 1

v = 0, J ”= 0

F’ = 1/2

F’ = 5/2

F’ = 3/2

F” = 3/2

R(0)

measurement conditions●sweep step; 0.01 Hz/step (13.1 kHz/step in the mid-infrared frequency)●averaged over 20 frequency sweeps ●sweep time; 20 ms/step ●pressure; a few mTorr 　 ● measurement time; 20 min.●linewidth (HWHM); 230 kHz

F’ = 3/2

F’ = 5/2

F’ = 1/2

*

**

*cross-over resonance

Spin of Cl nuclear

*

*cross-over resonance

*×2***

**

☆ΔF ＝＋ 1, ☆ΔF ＝ 0

☆☆☆

☆

☆ ☆ ☆

☆☆

☆

☆ ☆☆

Observed spectra of H35Cl

**

*×2 *×2

R(1) R(2)

☆

☆

☆

☆☆

☆☆

☆ ☆☆

☆*×2*×2 ***×2 *×2**

R(3) R(4)

Hamiltonian

8

• Vibration energy

• Rotation energy

• Electric quadrupole hyperfine interaction

• Magnetic hyperfine interaction

v: vibrational quantum numberJ: rotational quantum numberBv: rotational constantDv: centrifugal distortionHv, Lv: high order centrifugal distortionI: nuclear spin quantum numberF: total angular momentum

vibrational term value

quadrupole coupling constant

magnetic coupling constant

Hamiltonian

9

• Vibration energy

• Rotation energy

• Electric quadrupole hyperfine interaction

• Magnetic hyperfine interaction

vibrational term value

quadrupole coupling constant

magnetic coupling constant

0 Relative Freq.(reference)

f1 f2

10

Determined molecular constants

• Analysis: Least-squares method• DATA: H35Cl; 42 hyperfine-resolved transitions of R(0) to R(4) H37Cl; 35 hyperfine-resolved transitions of R(0) to R(3)• The ground state constants are fixed at the values determined by

Cazzoli*.• L1 is fixed at zero.• The weight is taken 1 for all hyperfine-resolved transitions and 0 for unresolved lines. *G. Cazzoli, et. al , JMS 266, 161 (2004)

v = 0 (sub-milli-

meter data)

v = 1

11

H35Cl: R(0) transition

: Upper level : Lower level

• The difference of the comb mode number is determined from HITRAN2008.• The uncertainly is typically 10 kHz for the lines with S/N higher than 4.• The pressure shift is less than the measurement uncertainty.

• All ΔF = ±1, 0 transitions are observed.

, ,

uncertainty=√ (fitting uncertainty )2+ (statistical uncertainty )2

: Upper level : Lower levelH35Cl: R(1) transition

• All ΔF = +1, 0 transitions are observed.• Any ΔF = –1 transitions are not observed, but the frequencies can be experimentally determined.

: weight 0*,𝐹 ′ 𝐽 ′ ,𝐹 ¿𝐽 ¿



: weight 0*: Upper level : Lower level,𝐹 ′ 𝐽 ′ ,𝐹 ¿𝐽 ¿

15


• All ΔF = +1 transitions are observed.• The frequencies of ΔF = 0 transitions are determined from that of the cross-over resonances.• The frequencies of ΔF = –1 transitions can be calculated.


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Determined molecular constants

*G. Cazzoli, et. al , JMS 266, 161 (2004)

*.• The standard deviation: 10.1 kHz

Summary• Transition frequencies of ΔF = ±1, 0 of R(0)-R(4) for H35Cl and

R(0)-R(3) for H37Cl are determined with a typical uncertainty of 10 kHz using the comb-referenced DFG spectrometer.

• Six molecular constants are determined with a standard deviation of 10.1 kHz.

• The absolute frequency measurements and the assignment of absorption lines are consistent, and the model Hamiltonian is accurate enough to reproduce the measured transition frequencies.

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AcknowledgmentsThis research is financially supported by Grand-in-Aid for Scientific Research (A), the Photon Frontier Network Program of the Ministry of Education, Culture, Sports, Science and Technology, and JST, ERATO, MINOSHIMA Intelligent Optical Synthesizer Project Japan.

Kana Iwakuni et. al, JMS 306 (2014) 19-25, Hyperfine-resolved transition frequency list of fundamental vibration bands of H35Cl and H37Cl

http://www.mext.go.jp/

http://www.photonfrontier.net/

K. Iwakuni, H. Sera, M. Abe, and H. Sasada Department of Physics, faculty of Science and Technology,...

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