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Rotational and Rotational-Vibrational Raman Spectroscopy of Air to Characterize Astronomical Spectrographs

F. Kerber, G. Lo Curto, P. Figueira, F. Pepe, D. Mťgevand, M. Riva, P. Di Marcantonio, C. Lovis, M. Amate, P. Molaro, A. Cabral, M.-R. Osorio

Abstract
Raman scattering enables unforeseen uses for the laser guide-star system of the Very Large Telescope. Here, we present the observation of one up-link sodium laser beam acquired with the ESPRESSO spectrograph at a resolution λ /∆ λ ̃140 000 . In 900 s on source, we detect the pure rotational Raman lines of 16O2, 14N2, and 14N 15N (tentatively) up to rotational quantum numbers J of 27, 24, and 9, respectively. We detect the 16O2 fine-structure lines induced by the interaction of the electronic spin S and end-over-end rotational angular momentum N in the electronic ground state of this molecule up to N =9 . The same spectrum also reveals the ν1 ←0 rotational-vibrational Q-branch for 16O2 and 14N2 14. These observations demonstrate the potential of using laser guide-star systems as accurate calibration sources for characterizing new astronomical spectrographs.

Keywords
Astrophysics - Instrumentation and Methods for Astrophysics; Physics - Atmospheric and Oceanic Physics; Physics - Instrumentation and Detectors

Physical Review Letters
Volume 123, Issue 6, Page 11
2019 August

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Instituto de Astrof√≠sica e Ci√™ncias do Espa√ßo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia