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-IR double resonance technique has been applied to pump the lower states and subsequently probe the hot bands. Two new hot bands, nu10 + nu11 - nu10 and nu7 + nu11 - nu7, have been found. The weak hot band starting from nu7 has been identified by direct labeling of some rotational levels in the nu7 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 nu9 + nu10 level has been reinvestigated and a b-type Coriolis interaction with the nearby nu7 + nu11 state has been observed. Rotational energy levels of nu7 + nu11 and of nu9 + nu10 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 nu10 + nu11 state, a global a-type Coriolis interaction with nu8 + 2nu12 has been identified.