Effective Rotation–Pseudorotation Hamiltonian forX3-Type Molecules: Application to theB̃–X̃Transition of Na3

✍ Scribed by Nobukimi Ohashi; Makiko Tsuura; Jon T. Hougen; Wolfgang E. Ernst; Stefan Rakowsky

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 387 KB
• Volume: 184
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1997.7306

✦ Synopsis

A formalism has been developed for rotation-pseudorotation energy levels of X 3 -type molecules in orbitally nondegenerate electronic states (so that Jahn-Teller complications are absent). The formalism includes electron spin, but excludes nuclear spin effects. Correlation diagrams are presented connecting rotational energy levels in the high-barrier asymmetric-rotor limit to those in the low-barrier free-rotor quasi-symmetric-top limit. By applying the formalism to the B ˜state of Na 3 , which exhibits nearly free pseudorotation, a global fit of 216 B ˜(u Å 1) -X ˜transitions to 15 molecular parameters was carried out, leading to a satisfactory standard deviation of 0.012 cm 01 . (The lower X ˜state was treated as a rigid asymmetric rotor.) The fit contains many j Å 0 levels and some j Å 1 levels, but only a few j Å 2 and j Å 3 levels, where j is the pseudorotation quantum number in the B ˜state. Inclusion of traditional spin-rotation terms did not improve the fit, but a phenomenological term coupling electron spin to the pseudorotation angular momentum was able to account for the large spin splittings observed in j ú 0 pseudorotational levels. Our ground state rotational constants are consistent with those determined by other workers from analysis of the A ˜-X ˜transition.