METHYL ISOCYANIDE HOT BANDS IN THE REGION 1300-1560 CM(-1)

The hot bands accompanying the fundamentals nu(6) and nu(3) of CH3NC i n the region 1300-1560 cm(-1) observed in high-resolution Fourier tran sform recordings complemented by diode laser spectra have been analyze d. The observed transitions comprise 16 subbands of the pair of perpen dicular E-E bands nu(6)(+/-) + nu(8)(+/-) - nu(8)(+/-) and nu(7)(-/+) + 2 nu(8)(0) - nu(8)(+/-) whose upper states form a Fermi dyad, 18 sub bands of the A(1,2)-E perpendicular bands nu(6)(-/+) + nu(8)(+/-) - nu (8)(+/-)/nu(7)(+/-) + 2 nu(8)(+/-2) - nu(8)(+/-) with upper states for ming another Fermi dyad, and 8 subbands of the bi-parallel E-E band nu (3) + nu(8)(+/-) - nu(8)(+/-). The anharmonic, Coriolis, and l-type in teractions which couple these upper states with each other and with th e states nu(7)(-/+) + 2 nu(8)(+/-2), nu(4) + 3 nu(8)(+/-1), and nu(4) + 3 nu(8)(+/-3) have been included in an 18 x 18 Hamiltonian matrix wh ose eigenvalues model the upper levels of the observed transitions. Th e values of 46 upper state spectroscopic constants and interaction con stants have been adjusted by least squares to 950 observed lines. The results provide a reliable quantitative picture of the interacting sta tes and yield accurate values for the spectroscopic constants of the v arious states and for the anharmonic constants (x(68)), x(68) (g(68)), and x(38). (C) 1997 Academic Press.