Speaker
Description
We introduce, for the first time, a spectrometer based on a high-finesse optical resonator operating in a deep cryogenic regime, i. e., below 5 K. This system enables uniform cooling of the entire optical cavity, including the gas sample, the mirrors as well as the piezoelectric actuator (with tunability range exceeding 20 μm [1]). The setup is designed in a way that efficiently attenuates both external vibrations and those originating from the cryocooler itself, ensuring stable operation of the optical cavity.
The spectrometer, integrated with an optical parametric oscillator (OPO), facilitates the investigation of the fundamental band of $\rm H_2$ in the range from 2.2 to 2.4 μm. We will demonstrate our first measurements of the rovibrational transition S(0) from 1-0 band in cold molecular hydrogen at 5 K in the Doppler-limited regime. Achieving accuracy at the level of $\rm 10^{-6}~cm^{-1}$, our system allows for testing of the quantum electrodynamics (QED) corrections for $\rm H_2$ at the fifth significant digit of the QED correction [2-3]. By saturating the very weak quadrupole transitions in $\rm H_2$ we expect to further enhance the accuracy by an order of magnitude. This is achievable thanks to the deep cryogenic regime of our cavity and high laser power provided by the OPO.
[1] M. Słowiński, M. Makowski, K. L. Sołtys, K. Stankiewicz, S. Wójtewicz, D. Lisak, M. Piwiński, P. Wcisło, Rev. Sci. Instrum. 93, 115003 (2022)
[2] J. Komasa, M. Puchalski, P. Czachorowski, G. Łach, and K. Pachucki, Phys. Rev. A 100, 032519 (2019)
[3] P. Czachorowski, M. Puchalski, J. Komasa, and K. Pachucki, Phys. Rev. A 98, 052506 (2018)
