10min:

TINA ERICA ODAKA, TSUNEO HIRANO, Department of Chemistry, Faculty of Science, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan; PER JENSEN, Institute for Astrophysics and Planetary Sciences, Ibaraki University, 2-1-1 Bunkyo, Mito 310-8512, Japan.

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In 1986 Guélin et al. \footnoteM. Guélin, J. Cernicharo, C. Kahane, and J. Gomez-Gonzales, Astronomy~&~Astrophysics 157, L19 (1986) found, in radio astronomical observations, six transitions originating in the circumstellar envelope of the late-type carbon star IRC+10216. No assignment of these lines could be given at the time, but they were later identified \footnoteK. Kawaguchi, E. Kagi, T. Hirano, S. Takano, and S. Saito, Astrophys.~J. 406, L39 (1993) ^, \footnoteK. Ishii, T. Hirano, U. Nagashima, B. Weis and K Yamashita, Astrophys.~J. 410, L43 (1993) as belonging to the rotational spectrum of the MgNC radical. Thus, MgNC became the first Mg-containing molecule to be identified in interstellar space. The only rotationally resolved, spectroscopic data presently available for ^{2 +} MgNC comprise the rotational spectrum ^c, \footnoteM.~A.~Anderson and L.~M.~Ziurys, Chem.~Phys.~Lett. 231, 164 (1994); E.~Kagi, K.~Kawaguchi, S.~Takano, and T.~Hirano, J.~Chem.~Phys. 104, 1263 (1996) together with a few vibronic bands, all originating in the vibronic ground state and belonging to the ^{2 2 +} electronic transition. \footnoteR.~R.~Wright and T.~A.~Miller, J.~Mol.~Spectrosc. 194, 219 (1999) In the hope of stimulating further characterization of ^{2 +} MgNC by high resolution spectroscopy, we report here ab initio simulations of its lowest -state rotation-vibration bands. The calculations are carried out with the MORBID program system, and they are based on a previously calculated potential energy function using ACPF method, supplemented with dipole moment surfaces computed with CASSCF/[TZ3P+f(Mg), aug-cc-pVQZ(N andC)].