  Ground-based optical astronomical observations supported by or in the
vicinity of laser guide-star systems can be contaminated by Raman-scattered
laser photons. Anticipating, alleviating, and correcting for the impact of this
self-inflicted contamination requires a detailed knowledge of the
pure-rotational and rotational-vibrational spectrum of the molecules in our
atmosphere. We present a 15.3hr-deep combined spectrum of the 4LGSF's 589nm
$\approx$ 509THz sodium laser beams of Paranal observatory, acquired with the
ESPRESSO spectrograph at a resolution
$\lambda/\Delta\lambda\cong140'000\approx0.12$ cm$^{-1}$ and an altitude of 23
km above mean sea level. We identify 865 Raman lines over the spectral range of
[3770; 7900]{\AA}$\approx$[+9540; -4315] cm$^{-1}$, with relative intensities
spanning ~5 orders of magnitudes. These lines are associated to the most
abundant molecules of dry air, including their isotopes: 14N14N, 14N15N,
16O16O, 16O17O, 16O18O, and 12C16O16O. The signal-to-noise of these
observations implies that professional observatories can treat the resulting
catalogue of Raman lines as exhaustive (for the detected molecules, over the
observed Raman shift range) for the purpose of predicting/correcting/exploiting
Raman lines in astronomical data.
  Our observations also reveal that the four laser units of the 4LGSF do not
all lase at the same central wavelength. [...] The [measured] offsets [...] are
larger than the observed 4LGSF spectral stability of $\pm$3 MHz over hours.
They remain well within the operational requirements for creating artificial
laser guide-stars, but hinder the assessment of the radial velocity accuracy of
ESPRESSO at the required level of 10 m/s. Altogether, our observations
demonstrate how Raman lines can be exploited by professional observatories as
highly-accurate, on-sky wavelength references.
