The ethylene hot band spectrum near 3000 cm(-1)

A new hot band spectrum of ethylene has been recorded from 2970 to 3015 cm(-1) at low rotational temperatures in a seeded molecular jet, using vibrational energy transfer from SF6 to C2H4. An IR-LR double resonance technique has been applied to pump the lower states and subsequently probe the hot bands. Two new hot bands, nu(10) + nu(11) - nu(10) and nu(7) + nu(11) - nu(7), have been found. The weak hot band starting from nu(7) has been identified by direct labeling of some rotational levels in the nu(7) manifold. High resolution FTIR spectra at ambient and at elevated temperatures have been recorded, too; it has thus become possible to extend the analysis to higher rotational quantum numbers. The previously analyzed nu(9) + nu(10) level has been reinvestigated and a b-type Coriolis interaction with the nearby nu(7) + nu(11) state has been observed. Rotational energy levels of nu(7) + nu(11) and of nu(9) + nu(10) have been fitted simultaneously, taking into account the local perturbations due to five dark states. From the shift of all K not equal 0 levels to higher frequencies in the nu(10) + nu(11) state, a global a-type Coriolis interaction with nu(8) + 2 nu(12) has been identified. (C) 1996 Academic Press, Inc.