ExoMol line lists -- LIV: Empirical line lists for AlH and AlD and experimental emission spectroscopy of AlD in $A$ $^1\Pi$ ($v=0, 1, 2$)
arxiv(2023)
摘要
New ExoMol line lists AloHa for AlH and AlD are presented improving the
previous line lists WYLLoT (Yurchenko et al., MNRAS 479, 1401 (2018)). The
revision is motivated by the recent experimental measurements and astrophysical
findings involving the highly excited rotational states of AlH in its
$A\,^{1}\Pi-{X}\,^{1}\Sigma^{+}$ system. A new high-resolution emission
spectrum of ten bands from the ${A}\,^{1}\Pi-{X}\,^{1}\Sigma^{+}$ system of
AlD, in the region $17300 - 32000$ cm$^{-1}$ was recorded with a Fourier
transform spectrometer, which probes the predissociative $A\,^1\Pi$ $v=2$
state. The AlD new line positions are combined with all available experimental
data on AlH and AlD to construct a comprehensive set of empirical rovibronic
energies of AlH and AlD covering the $X\,^1\Sigma^+$ and $A\,^1\Pi$ electronic
states using the MARVEL approach. We then refine the spectroscopic model WYLLoT
to our experimentally derived energies using the nuclear-motion code Duo and
use this fit to produce improved line lists for $^{27}$AlH, $^{27}$AlD and
$^{26}$AlH with a better coverage of the rotationally excited states of
$A\,^1\Pi$ in the predissociative energy region. The lifetimes of the
predissociative states are estimated and are included in the line list using
the new ExoMol data structure, alongside the temperature-dependent continuum
contribution to the photo-absorption spectra of AlH. The new line lists are
shown to reproduce the experimental spectra of both AlH and AlD well, and to
describe the AlH absorption in the recently reported Proxima Cen spectrum,
including the strong predissociative line broadening. The line lists are
included into the ExoMol database www.exomol.com.
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