Sub-MHz accuracy measurement of the S(2) 2–0 transition frequency of D2 by Comb-Assisted Cavity Ring Down spectroscopy

Abstract

The line position of the very weak S(2) transition of deuterium in the 2-0 band has been measured with a Comb-Assisted Cavity Ring Down spectrometer.The high sensitivity spectra were recorded at 5 and 10 mbar with a Noise Equivalent Absorption, a min ,of 8Â 10 -11 cm À1 . The line positions at 5 and 10 mbar were measured with sub-MHz accuracy (460 and 260 kHz, respectively). After correction of the line pressure-shift, the frequency at zero pressure of the S(2) transition of the first overtone band was determined to be 187 104 299.51 ± 0.50 MHz. This value agrees within 1.7 MHz with the frequency obtained from the best available ab initio calculations and corresponds to only 15% of the claimed theoretical uncertainty.

Ultrahigh finesse cavity-enhanced spectroscopy for accurate tests of quantum electrodynamics for molecules

“…Previous experiment, combined Refs. [10,11] 6241.127 647 (11) 3. This work 6241.127 667 0(54) V. ACKNOWLEDGEMENTS NS, HJ and PW contribution is supported by the National Science Centre in Poland through project no.…”

“…Furthermore, molecular hydrogen possesses a wide structure of ultra-narrow rovibrational transitions [5] with different sensitivities to the proton charge radius and proton-to-electron mass ratio. Therefore, the recent large progress in both theoretical [1, 2,6] and experimental [7][8][9][10][11] determinations of the rovibrational splitting in different isotopologues of molecular hydrogen makes it a promising system for adjusting several physical constants [12,13]. The most accurate measurements were performed for the HD isotopologue with absolute accuracy claimed to be 20 kHz [14] and 80 kHz [8] for the R(1) 2-0 line.…”

Absolute frequency determination of molecular transition in the Doppler regime at kHz level of accuracy

“…The proposed technique can be used for accurate measurements of line positions and collisional shift coefficients for lines which are crucial for fundamental science and cannot be easily accessed by Doppler-free techniques, such as weak hydrogen lines [5]. Frequency measurements of these transitions find applications in verification of quantum electrodynamics in molecular systems for which high-accuracy ab initio calculations are possible [40].…”

“…Spectroscopy of weak molecular transitions, like the O 2 B-band [4] line presented here or the quadrupole transitions in H 2 or D 2 [5], can provide valuable information about molecular structure [6] or verify quantum electrodynamics in molecular systems [7]. Unfortunately, Doppler-free techniques in gas cells or even in optical cavities cannot be applied for such transitions.…”

Accurate wavenumber measurements for the S0(0), S0(1), and S0(2) pure rotational Raman lines of D2

“…The main obstacle to obtain accurate experimental data on the H 2 isotopologues is the absence (or in the case of HD, the small magnitude) of a dipole moment, which limits the techniques that can be used to either Raman spectroscopy or ultrasensitive absorption techniques that allow the observation of the extremely weak quadrupole or collision‐induced transitions (weak dipole transitions for HD). The availability of such techniques has prompted, in recent years, the completion of a number of studies on these molecules . Specifically, most of them have used cavity ring‐down spectroscopy or cavity‐enhanced saturated absorption to measure quadrupole and collisionally induced rovibrational transitions in the first and second overtones of H 2 , HD, and D 2 .…”