Mid-infrared Doppler-free Saturation Absorption Spectroscopy Of Methane For Future Cavity-enhanced Double-resonance Spectroscopy Investigating Its High Polyads.

Riyadh, S. M. Shah

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https://hdl.handle.net/2142/116930 Copy

Description

Title

Mid-infrared Doppler-free Saturation Absorption Spectroscopy Of Methane For Future Cavity-enhanced Double-resonance Spectroscopy Investigating Its High Polyads.

Author(s)

Riyadh, S. M. Shah

Contributor(s)

• Liu, Jinjun
• Islam, Md Touhidul
• Telfah, Hamzeh

Issue Date

2022-06-23

Keyword(s)

Structure determination

Abstract

Understanding the rotational structure of molecular spectra requires high resolution and high-frequency accuracy. Furthermore, a capability of high-speed, wide-range spectral scan is strongly desired. We have developed a mid-infrared Doppler-free saturation absorption spectroscopy apparatus using a continuous-wave optical parametric oscillator (CW-OPO).\footnote{D. B. Foote, M. J. Cich, W. C. Hurlbut, U. Eismann, A. T. Heiniger, and C. Haimberger, ``High-resolution, broadly-tunable mid-IR spectroscopy using a continuous-wave optical parametric oscillator'' \textit{Opt. Express} \textbf{29}, 5295-5303 (2021)} Here we report a comprehensive spectral scan of the $\nu_3 = 1$ band of methane (CH$_4$). The absolute frequency calibration was achieved using previously reported transition frequencies determined using optical frequency combs,\footnote{M. Abe, K. Iwakuni, S. Okubo, and H. Sasada, ``Accurate transition frequency list of the $\nu_3$ band of methane from sub-Doppler resolution comb-referenced spectroscopy,'' \textit{J. Opt. Soc. Am. B} \textbf{30}, 1027-1035 (2013)} while a home-build Fabry-P\'{e}rot etalon was used for relative frequency calibration. A linewidth of less than 5 MHz has been reached, and the frequency accuracy is estimated to be better than 1 MHz, both of which can be further improved. We have successfully locked the frequency of the OPO to a Doppler-free line of CH$_4$ using a top-of-fringe locking method. A cavity-enhanced double-resonance spectroscopy apparatus is under construction. It combines the Doppler-free saturation absorption setup and an existing continuous-wave cavity ring-down (CW-CRDS) spectroscopy apparatus. The first mid-infrared photon from the frequency-locked OPO pumps the CH$_4$ molecule to the $\nu_3 = 1$ vibrational levels, followed by a further excitation to high polyads using a Ti:Saphire ring laser.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116930

DOI

https://doi.org/10.15278/isms.2022.RL11

Copyright and License Information

Copyright 2022 held by the authors

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