An ab initio prediction of the spectroscopic constants of MgNC - The first Mg-bearing molecule in space

High-Resolution, Rotationally Resolved Electronic Spectroscopy of the MgNC Radical

“…For MgNC, the linear structure first predicted by Bauschlicher and co-workers (8) and in subsequent theoretical studies (4,5,17) was first confirmed by Kawaguchi's spectrum (2), which determined that indeed the X state was a linear 2 ⌺ ϩ state. Experimental evidence that the isocyanide structure was more stable than the cyanide molecule was found by Ziurys et al (6) from the MgNC/MgCN ratio of ϳ22/1 derived from the interstellar spectral data from IRCϩ10216.…”

“…That same year, Guélin and co-workers interpreted the interstellar spectrum, now with the spectroscopic constants obtained by Kawaguchi et al, and they were able to assign the observed emission lines to MgNC (3). The identification of the carrier of Kawaguchi's spectrum was supported by ab initio studies by Ishii and co-workers (4,5), who carried out CISD/ TZ2P calculations on the ground electronic state. In addition, MgCN, the metastable isomer of MgNC, has also been detected (6) in the star IRCϩ10216 in 1995, one year after its laboratory identification by Anderson et al (7).…”

“…The two remaining bands referred to as "Band A" and "Band B" in the following occur at lower frequency than the 3 0 1 transition, so they can only be fundamentals or overtones of 2 , the bending mode, since 1 is expected (4,17,20) to be above 2000 cm Ϫ1 . The assignment to which particular levels in the bending mode these transitions terminate, however, is not that straightforward.…”

An ab Initio Study of the Ã2Π State and the Ã2Π←X̃2Σ+ Electronic Transition of MgNC

“…(14). The differences are believed to be caused by a difference between 3 The potential energy fucntions of Ref. (15) are incorrectly quoted by Taketsugu and Carter (14) in that the basis set employed for Mg is not TZ2P + f, but TZ3P + f, and their Eq.…”

“…(1), which reports the detection of six initially unassigned lines in the circumstellar envelope of the late-type carbon star IRC + 10216, together with Refs. (2,3), in which these lines are assigned as belonging to the rotational spectrum of MgNC), and this has stimulated significant interest in this radical (see, for example, Refs. (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)).…”