MASARU FUKUSHIMA AND TAKASHI ISHIWATA, Faculty of Information Sciences, Hiroshima City University, Asa-Minami, Hiroshima 731-3194, Japan.
We have generated MgNC in supersonic free jet expansions, and measured the laser induced fluorescence excitation spectra of the Mg-N-C bending vibronic bands of the A 2 -- X 2 + transition. In addition to the two vibronic bands, 201, 2 ^(+) -- and 202, 2 -- 2 +, reported by Wright and Miller, the 202, µ 2 _\frac12 -- 2 + sub-band were found just above the 201 vibronic band. The most remarkable feature of this newly observed sub-band is unexpected rotational structure on the upper vibronic level, A (020) µ 2 _\frac12; i.e.~the rotational levels show splitting into the e and f sub-levels and have different rotational constants on the each rotational sub-level. Introducing the Coriolis coupling terms of -J\pmG\mp and S\pmG\mp, which could be called the G-uncoupling operator and the spin-Coriolis interaction, respectively, into the rotational Hamiltonian, this unexpected rotational structure has been analyzed quite reasonably.