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A new linelist (list of wavelengths with corresponding intensities) for the diatomic molecule Chromium Hydride, CrH and its various isotopologues has been created within the ExoMol project (http://exomol.com/). The ExoMol methodology comprises of performing high-level ab initio calculations followed by refinement to available experimental data.

CrH is of interest in the modelling of L-type Brown Dwarfs: a creation of a new linelist for CrH has been clearly required due to the problems with correctly modeling the opacity of these objects (Lyubchik et al. 2007). Furthermore, it has also been proposed that CrH and CrD could be used in the so-called “deuterium test” which aims to distinguish between brown dwarfs and large planets (Pavlenko et al. 2008).

Our new linelist includes 8 electronic states and ~80, 000 rovibronic states and ~11 million transitions. Potential Energy curves for the A and X states have been refined to 0.04 cm-1 and 1.52 cm-1 for the (0, 0) band and ~2 cm$ cm-1 for the (1, 0) band. Our linelist has a wavelength coverage from around 10 to 0.5 microns: our vibrational and J coverage supersedes that of the linelist of Burrows et al. (2002) which is for only the first 2 electronic states (X and A). We have shown that our linelist is adequate up to around ~3000 K which opens up the possibility of detection on exoplanets using telescopes such as the JWST.

References
J. Tennyson, S. N. Yurchenko, A. F. Al-Refaie, E. J. Barton, K. L. Chubb, P. A. Coles, S. Diamantopoulou, M. N. Gorman, C. Hill, A. Z. Lam, L. Lodi, L. K. McKemmish, Y. Na, A. Owens, O. L. Polyansky, C. Sousa-Silva, D. S. Underwood, A. Yachmenev, E. Zak, "The ExoMol database: molecular line lists for exoplanet and other hot atmospheres", Journal of Molecular Spectroscopy 327, 73-94 (2016)

J. Tennyson, S. N. Yurchenko, "ExoMol: molecular line lists for exoplanet and other atmospheres", Monthly Notices of the Royal Astronomical Society 425, 21-33 (2012)

Pavlenko, Y. V., Harris, G. J., Tennyson, J., Jones, H. R. A., Brown, J, M., Hill, C., Yakovina, L. A., "The electronic bands of CrD, CrH, MgD and MgH: application to the `deuterium test'", Monthly Notices of the Royal Astronomical Society 386, 1338-1346 (2008)

Y. Lyubchik, H. R. A. Jones, Y. V. Pavlenko, E. Martin, I. S. Mclean, L. Prato, R. J. Barber, J. Tennyson, "Spectral analysis of high resolution near-infrared spectra of ultra cool dwarfs", Astronomy & Astrophysics 473, 257-264 (2007)

A. Burrows, R. S. Ram, P. Bernath, C. M. Sharp, J. A. Milsom, "New CrH opacities for the study of L and brown dwarf atmospheres", Astrophysical Journal 577, 986-992 (2002)