'International Symposium on Molecular Spectroscopy'
Abstract
Around 398~nm, the jet-cooled rmNO2 spectrum exhibits a
well identified dissociation threshold (D0). Combining LIF detection
and continuous-wave absorption-based CRDS technique a frequency range
of simrm25,cm−1 is analyzed at high resolution around
D0. In addition to the usual rovibronic transitions towards
long-lived energy levels, sim115 wider resonances are observed.
Over this energy range, the resonance widths spread from simrm0.006,cm−1
(sim450:rmps) to simrm0.7,cm−1 (rmsimrm4:ps)
with large fluctuations. At least two ranges of resonance width can
be identified when increasing the excess energy. They are associated
with the opening of the dissociation channels rmNO2rightarrowrmNOleft(X,2Pi1/2,,v=0,,J=1/2right)+rmOleft(3P2right)
and rmNO2rightarrowrmNOleft(X,2Pi1/2,,v=0,,J=3/2right)+rmOleft(3P2right).
Weighted mean unimolecular dissociation rate coefficients kmathituni
are calculated. The density of reactants (following the RRKM predictions)
is deduced, and it will be discussed versus the density of transitions,
the density of resonances and the density of vibronic levels. The
data are analyzed in the light of time-resolved data previously reported.
This analysis corroborates the existence of loose transition states
along the reaction path close to the dissociation energy in agreement
with the phase space theory predictionsfootnote{[Accpeted in J. Chem. Phys.]}