Frequency comb referenced spectroscopy of A-X 0-0 transitions in SH.

We report absolute transition frequencies for the allowed transitions from the XΠ, v = 0, J″ = 3/2 rovibronic ground state of SH to the AΣ, v = 0 vibronic state. The frequencies have been determined with an uncertainty of less than 1 MHz, representing a more than 1000-fold improvement over previous measurements. Spectral traces are measured by scanning a frequency comb stabilized continuous-wave spectroscopy laser over the molecular transitions and detecting laser-induced fluorescence from SH molecules in a highly collimated molecular beam.

Sub-ppb Measurement of a Fundamental Band Rovibrational Transition in HD.

We report a direct measurement of the 1-0 R(0) vibrational transition frequency in ground-state hydrogen deuteride (HD) using infrared-ultraviolet double resonance spectroscopy in a molecular beam. Ground-state molecules are vibrationally excited using a frequency comb referenced continuous-wave infrared laser, and the excited molecules are detected via state-selective ionization with a pulsed ultraviolet laser. We determine an absolute transition frequency of 111 448 815 477(13) kHz.