Volume 130, Issue 4, 28 January 2009
Index of content:
130(2009); http://dx.doi.org/10.1063/1.3071199View Description Hide Description
We consider reversible breaking of adhesionbonds or folding of proteins under the influence of a constant external force. We discuss the statistical properties of the unbinding/rebinding events and analyze their mean number and their variance in the framework of simple kinetic models. In the calculations, we explicitly exploit the analogy to single molecule fluorescence and particularly between unbinding/rebinding and photon emission events. Whereas for two-state behavior Poisson or sub-Poisson statistics of the events is found, we show that for more general kinetic schemes also super-Poisson statistics can occur. Temporal fluctuations of the transition rates, a hallmark for the presence of dynamic disorder, should become experimentally accessible via the determination of the second moment of the event-number distribution.
130(2009); http://dx.doi.org/10.1063/1.3068334View Description Hide Description
The center-of-mass kinetic energy release for the dissociation of following charge exchange of with cesium has been studied experimentally and modeled using quasiclassical trajectory calculations based on an ab initio potential energy surface for and “direct dynamics” for . Branching fractions for the and dissociation channels have been measured and compared to the calculations. The dominant channel is found to be and the experimental kinetic energy release spectrum reveals that is formed with a vibrational inversion in stretching vibrations, coupled with low bending and rotational excitation.
130(2009); http://dx.doi.org/10.1063/1.3074100View Description Hide Description
The anharmonic vibronic absorptionspectrum of the formaldehyde molecule is computed on the fly using semiclassical dynamics. This first example of an on-the-fly semiclassical computation of a vibronic spectrum was achieved using a unit prefactor modified frozen Gaussian semiclassical propagator for the excited state. A sample of 6000 trajectories sufficed for obtaining a converged spectrum, which is in reasonable agreement with experiment. Similar agreement is not obtained when using a harmonic approximation for the spectrum, demonstrating the need for a full anharmonic computation. This first example provides a resolution of . Potential ways of improving the methodology and obtaining higher resolution and accuracy are discussed.