Accurate transition frequency list of the ν_3 band of methane from sub-Doppler resolution comb-referenced spectroscopy

Abstract

We have carried out sub-Doppler resolution spectroscopy of the ν 3 band of 12 CH 4 using a difference-frequencygeneration source, an enhanced cavity absorption cell, and an optical frequency comb, and we have added 150 lines to the transition frequency list published earlier [Opt. Express 19, 23878 (2011)]. It now covers 204 lines from the P12 to R8 transitions, involving 21 weak forbidden transitions, with a typical uncertainty of 3 kHz for allowed transitions and 12 kHz for forbidden transitions. The combination differences between the allowed and forbidden transitions enable us to determine a scalar rotational constant and three scalar distortion constants of the ground vibrational state with greatly reduced uncertainties.

Design of cavity-enhanced absorption cell for reducing transit-time broadening

“…This fact allows us to employ a new design of CEAC, which consists of concave and convex mirrors with in-stock radius of the curvature. The new CEAC narrows the observed Lamb dips in comparison with previous works [4][5][6][7].…”

“…The idler frequency is swept once at a rate of 10 Hz by applying triangle voltage to the PZT of the CEAC, while the idler frequency is stabilized at a certain cavity mode of the CEAC by the PDH technique. The horizontal axis, which is the elapsed time, is calibrated based on the absolute frequencies of the three components determined in the previous work [6] with uncertainties of 3 kHz, assuming that the idler frequency varies in proportion to the elapsed time. The typical linewidth of the recorded Lamb dips is 80 kHz (HWHM), which is one-third that recorded using the previous CEAC coupled with a Gaussian beam with a beam radius of 0.71 mm at the beam waist [5].…”

New investigation of the ν3 C–H stretching region of 12CH4 through the analysis of high temperature infrared emission spectra

“…This strong band was extensively studied in the literature and thus many data can be found. Before starting the analysis of the high temperature ν 3 emission spectra, we added 150 highly accurate transitions (3 kHz) from sub-Doppler resolution comb-referenced spectroscopy published by Abe et al [63]. These data, even limited rotationally to J = 14, bring strong additional constraints to the effective model essentially in the Pentad interacting states.…”

Fully stabilized mid-infrared frequency comb for high-precision molecular spectroscopy

“…[31] The small deviation of our result from that of Ref. [30] is likely due to the limited signal-to-noise ratio and due to systematic (technical) frequency shifts, which were not characterized for our setup.…”