Toward a Determination of the Proton-Electron Mass Ratio from the Lamb-Dip Measurement of HD

Abstract

Precision spectroscopy of the hydrogen molecule is a test ground of quantum electrodynamics (QED), and it may serve for the determination of fundamental constants. Using a comb-locked cavity ring-down spectrometer, for the first time, we observed the Lamb-dip spectrum of the R(1) line in the overtone of hydrogen deuteride (HD). The line position was determined to be 217 105 182.79±0.03_{stat}±0.08_{syst} MHz (δν/ν=4×10^{-10}), which is the most accurate rovibrational transition ever measured in the ground electronic state of molecular hydrogen. Moreover, from calculations including QED effects up to the order m_{e}α^{6}, we obtained predictions for this R(1) line as well as for the HD dissociation energy, which are less accurate but signaling the importance of the complete treatment of nonadiabatic effects. Provided that the theoretical calculation reaches the same accuracy, the present measurement will lead to a determination of the proton-to-electron mass ratio with a precision of 1.3 parts per billion.

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

“…Such accuracy was obtained by saturating the transition and measuring the sub-Doppler structure. These two results [8,14] differ, however, by almost 1 MHz. Recently, it was reported [7] that the uncertainty from Ref.…”

“…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.…”

Precision tests of nonadiabatic perturbation theory with measurements on the DT molecule

“…[20][21][22]) and the mixed isotopologue HD (cf. [23][24][25][26]). On the other hand, very few precision studies have been undertaken on the tritium-bearing species [27][28][29], on account of difficulties in handling radioactive tritium.…”

Frequency metrology of molecules in the near-infrared by NICE-OHMS

“…Precise frequency measurements of molecular transitions play an essential role in widespread applications, such as frequency metrology [1], astronomy [2,3], and molecular spectroscopy [4,5]. There are also increasing interests to use precise molecular transitions to test the quantum electrodynamics (QED) theory [6][7][8], to determine fundamental physical constant [9] or to verify its stability [10][11][12][13], and to search parity-violating effects in chiral molecules [14,15]. Moreover, reliable molecular frequencies are also candidates for optical clocks [16].…”