The NO Dimer: Jet-Cooled Study of nu1 and nu5 Transitions

The symmetric nu1 and antisymmetric nu5 vibrations of (NO)2 have been recorded at very low rotational temperature (4 K) using a molecular jet coupled with a high-resolution Fourier transform spectrometer (Bruker IFS 120 HR). A White-type multipass setup allowed us to record the very weak absorption of this dimer. A vibrational predissociation time equal to 75 ps was measured for the nu5 band, in good agreement with values directly derived from photodissociation measurements. This result shows that previous data obtained from spectra recorded using a low-temperature cell at thermodynamical equilibrium were distorted under the effect of molecular collisions. Copyright 1998 Academic Press.