Lamb-dip spectroscopy of buffer-gas-cooled molecules

Year: 2019

Authors: Di Sarno V., Aiello R., De Rosa M., Ricciardi I., Mosca S., Notariale G., De Natale P., Santamaria L., Maddaloni P.

Autors Affiliation: CNR-INO, Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy; INFN, Istituto Nazionale di Fisica Nucleare, Sez. di Napoli, Complesso Universitario di M.S. Angelo, Via Cintia, 80126 Napoli, Italy; CNR-INO, Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, Italy; INFN, Istituto Nazionale di Fisica Nucleare, Sez. di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy; ASI, Agenzia Spaziale Italiana, Contrada Terlecchia, 75100 Matera, Italy

Abstract: Nowadays, buffer-gas cooling represents an invaluable option to produce cold stable molecules, both in view of secondary cooling/trapping strategies towards the achievement of quantum degeneracy and for fundamental studies of complex molecules. From this follows a demand to establish a pool of specialized, increasingly precise spectroscopic interrogation techniques. Here, we demonstrate a general approach to Lamb-dip ro-vibrational spectroscopy of buffergas-cooled molecules. The saturation intensity of the selected molecular transition is achieved by coupling the probe laser to a high-finesse optical cavity surrounding the cold sample. A cavity ring-down technique is then implemented to perform saturation sub-Doppler measurements as the buffer (He) and molecular gas flux are varied. As an example, the ν1  ν3 R(1) ro-vibrational line in a 20 Kelvin acetylene sample is addressed. By referencing the probe laser to a Rb/GPS clock, the corresponding line-center frequency as well as the self and foreign (i.e., due to the buffer gas) collisional broadening coefficients are absolutely determined. Our approach represents an important step towards the development of a novel method to perform ultra-precise ro-vibrational spectroscopy on an extremely wide range of cold molecules. In this respect, we finally discuss a number of relevant upgrades underway in the experimental setup to considerably improve the ultimate spectroscopic performance.

Journal/Review: OPTICA

Volume: 6 (4)      Pages from: 436  to: 441

KeyWords: Lamb-dip spectroscopy; buffer gas cooling; ring-down spectroscopy; radiocarbon dioxide; frequency; resolution; laser; band; NM
DOI: 10.1364/OPTICA.6.000436

Citations: 14
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