			15min:

NOVEL PATTERNS OF TORSION~-~INVERSION TUNNELING AND TORSION~-~ROTATION COUPLING IN THE

₁₁ CH~-~STRETCH REGION OF CH₃NH₂.

MAHESH B DAWADI, SYLVESTRE TWAGIRAYEZU, C. MICHAEL LINDSAY AND DAVID S. PERRY, Department of Chemistry, The University of Akron, OH 44325-3601; LI-HONG XU, Department of Physics, Centre for Laser, Atomic and Molecular Studies (CLAMS) University of New Brunswick, Saint John, New Brunswick, Canada E2L 4L5.

The high-resolution infrared spectrum of CH₃NH₂ has been recorded using slit-jet absorption spectroscopy in the ₁₁ asymmetric CH-stretch region (2965~to~3005 cm^-1) with resolution of 0.003 cm^-1. The 580 lines, assigned by ground state combination differences, represent 27 subbands with |K'| \leq 2 for the A, B, E₁ and E₂ symmetries. Several of the observed subbands are split by perturbations. The analysis of spectrum shows that the patterns of the torsion-inversion tunneling splittings are qualitatively different from the ground state. In addition, the low - J splittings between |K'| =~ +|K'| and -|K'| are greatly reduced relative to the ground state in both the E₁ and the E₂ species, indicating that torsion-rotation coupling is suppressed in the ₁₁ CH-stretch excited state.