THE ETHYLENE HOT-BAND SPECTRUM NEAR 3000 CM(-1)

A new hot band spectrum of ethylene has been recorded from 2970 to 301 5 cm(-1) at low rotational temperatures in a seeded molecular jet, usi ng vibrational energy transfer from SF6 to C2H4. An IR-LR double reson ance technique has been applied to pump the lower states and subsequen tly probe the hot bands. Two new hot bands, nu(10) + nu(11) - nu(10) a nd 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 beco me possible to extend the analysis to higher rotational quantum number s. The previously analyzed nu(9) + nu(10) level has been reinvestigate d and a b-type Coriolis interaction with the nearby nu(7) + nu(11) sta te has been observed. Rotational energy levels of nu(7) + nu(11) and o f 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) sta te, a global a-type Coriolis interaction with nu(8) + 2 nu(12) has bee n identified. (C) 1996 Academic Press, Inc.