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

• Published in: Physical review letters 2019-08, Vol.123 (6), p.061101-061101, Article 061101
• Main Authors: Vogt, Frédéric P A, Kerber, Florian, Mehner, Andrea, Yu, Shanshan, Pfrommer, Thomas, Lo Curto, Gaspare, Figueira, Pedro, Parraguez, Diego, Pepe, Francesco A, Mégevand, Denis, Riva, Marco, Di Marcantonio, Paolo, Lovis, Christophe, Amate, Manuel, Molaro, Paolo, Cabral, Alexandre, Osorio, Maria Rosa Zapatero
• Format: Article
• Language: English
• Subjects: Angular momentum; Celestial bodies; Electron spin; Laser beams; Laser guide stars; Lasers; Quantum numbers; Raman spectra; Raman spectroscopy; Rotational spectra; Spectrographs; Stellar systems; Very Large Telescope
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.123.061101

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/Δλ∼140 000. In 900 s on source, we detect the pure rotational Raman lines of ^{16}O_{2}, ^{14}N_{2}, and ^{14}N^{15}N (tentatively) up to rotational quantum numbers J of 27, 24, and 9, respectively. We detect the ^{16}O_{2} 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 ν_{1←0} rotational-vibrational Q-branch for ^{16}O_{2} and ^{14}N_{2}. These observations demonstrate the potential of using laser guide-star systems as accurate calibration sources for characterizing new astronomical spectrographs.