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Using previous measurements and quantum chemical calculations to derive the molecular properties of the TiH molecule, we obtain new values for its ro-vibrational constants, thermochemical data, spectral line lists, line strengths, and absorption opacities. Furthermore, we calculate the abundance of TiH in M and L dwarf atmospheres and conclude that it is much higher than previously thought. We find that the TiH/TiO ratio increases strongly with decreasing metallicity, and at high temperatures can exceed unity. We suggest that, particularly for subdwarf L and M dwarfs, spectral features of TiH near $\sim$0.52 \mic, 0.94 \mic, and in the $H$ band may be more easily measureable than heretofore thought. The recent possible identification in the L subdwarf 2MASS J0532 of the 0.94 \mic feature of TiH is in keeping with this expectation. We speculate that looking for TiH in other dwarfs and subdwarfs will shed light on the distinctive titanium chemistry of the atmospheres of substellar-mass objects and the dimmest stars.Comment: 37 pages, including 4 figures and 13 tables, accepted to the Astrophysical Journa

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In this paper, we calculate new line lists and opacities for the 12 bands of the A$^6\Sigma^{+}$ -- X$^6\Sigma^{+}$ transitions of the CrH molecule. Identified in objects of the new L dwarf spectroscopic class (many of which are brown dwarfs), as well as in sunspots, the CrH molecule plays an important role in the diagnosis of low-temperature atmospheres. As a tentative first application of these opacities, we employ our new theoretical CrH data in an atmospheres code to obtain a CrH/H$_2$ number ratio for the skin of the L5 dwarf 2MASSI J1507038-151648 of $\sim 2-4\times 10^{-9}$, in rough agreement with chemical equilibrium expectations. Since in previous compilations the oscillator strength was off by more than an order of magnitude, this agreement represents a modest advance. However, in order to determine the CrH abundance in an L dwarf atmosphere, silicate clouds need to be incorporated into the model, and cloud modeling is still in a primitive stage of development. Nevertheless, one important step in L dwarf modeling is a reliable CrH opacity and this is what we have here attempted to provide.Comment: Includes 3 color figures (in .gif format). Accepted to the Astrophysical Journa

The emission spectrum of IrN has been investigated in the 10 000 -20 000 cm Ϫ1 region at 0.02 cm Ϫ1 resolution using a Fourier transform spectrometer. The bands were excited in an Ir hollow cathode lamp operated with a mixture of

Articles you may be interested inAb initio calculations on the X ̃ A ′ 1 and A ̃ A ″ 1 states of HPO and Franck-Condon simulation of the single vibronic level emission spectra of HPO and DPO A theoretical study of the excited states of CrH: Potential energies, transition moments, and lifetimes A theoretical study of the electronic structure and spectroscopic properties of the low-lying electronic states of the molecule SiB An ab initio study of CrC: A comparison of different levels of theory including density functional methodsThe spectrum of CrH has been reinvestigated in the 9000-15 000 cm Ϫ1 region using the Fourier transform spectrometer of the National Solar Observatory. The 1-0 and 1-1 bands of the A 6 ⌺ ϩ -X 6 ⌺ ϩ transition have been measured and improved spectroscopic constants have been determined. A value for the 2-0 band origin has been obtained from the band head using estimated spectroscopic constants. These data provide a set of much improved equilibrium vibrational and rotational constants for the A 6 ⌺ ϩ state. An accurate description of the A-X transition has been obtained using a multireference configuration interaction approach. The inclusion of both scalar relativity and Cr 3s3p correlation are required to obtain a good description of both states. The ab initio computed Einstein coefficients and radiative lifetimes are reported.

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