Time-dependent pump-probe spectra of NeBr2 -: art. no. 054311

Time- and frequency-resolved pump-probe measurements on NeBr2 have been performed to better characterize its fragmentation dynamics on the B electronic state for vibrational levels in the energy region of the transition from direct vibrational predissociation to intramolecular vibrational relaxation dynamics. Above nu(')=20 of the Br-2 stretching mode, it was observed that the dependence of lifetime on the vibrational quantum number deviates from the energy-gap law by leveling off in the range of 10 ps <tau < 20 ps. In addition to measuring the appearance of Br-2 product state levels, we were able to monitor the decay of the initially excited NeBr2 via B -> E transitions of the complex. These transitions are shifted 20 cm(-1) to lower energy from the free Br-2 resonances, indicating an E state Ne-Br-2 bond energy of 82 cm(-1). Measurements of NeBr2 vibrational predissociation via the Delta nu=-2 channel were also performed for nu(')=27, 28, and 29. The closing of the Delta nu=-1 channel leads to an increase in the lifetimes of these vibrational levels. A new Nd:yttrium aluminum garnet pumped dual optical parametric oscillator/optical parametric amplifier system is described that allows us to conveniently record time-delayed pump-probe spectra with 2-cm(-1) spectral resolution and 15-ps time resolution. (C) 2005 American Institute of Physics.