Index of content:
Volume 117, Issue 10, 08 September 2002
117(2002); http://dx.doi.org/10.1063/1.1504082View Description Hide Description
We outline a new time-dependent wave packet formulation of quantum scattering theory. The theory obtains the differential cross section directly from the time-evolution of a plane wave packet, bypassing the usual S-matrix formulas. We introduce the theory for potential scattering, generalize it to reactive scattering, then explain how the theory was used recently to interpret the reaction in collaboration with experiment [S. C. Althorpe, F. Fernández-Alonso, B. D. Bean, J. D. Ayers, A. E. Pomerantz, R. N. Zare, and E. Wrede, Nature (London) 416, 67 (2002)]. We also present new findings of quantum interference in the reaction.
117(2002); http://dx.doi.org/10.1063/1.1503310View Description Hide Description
Evaporative cooling, which is the usual mode of formation for many ion–molecule complexes, typically results in high internal energies. This in turn leads to a broadening of vibrational or vibronic spectra of these species. By incorporating argon into the nascent ion cluster, it is possible to significantly reduce the internal energy and thus simplify the spectra. This approach has been applied to the cluster ion. The binding of argon lowers the internal energy to an effective temperature of 125 K. Rotational structure in the asymmetric stretch can be analyzed to conclude that the structure of is quasi-linear with the heavy atoms in an configuration and the two hydrogen atoms symmetrically displaced off–axis, pointing away from the ion.
117(2002); http://dx.doi.org/10.1063/1.1503775View Description Hide Description
The principle of corresponding states is re-examined in the light of recent experimental and theoretical fluid equation of state data compilations. The results are used to critically test and extend the fundamental concept of corresponding states scaling for simple fluids (including rare gases, diatomics and methane). Classical corresponding states scaling based on critical point constants is found to produce weaker universal behavior than a new scaling procedure linked directly to the two intermolecular interaction potential parameters of a Lennard-Jones–6-12 fluid. The improved universal behavior revealed using this Lennard-Jones–corresponding-states scaling may either reflect inaccuracies in previous critical constant estimates, or perhaps point to more fundamental differences between the critical properties of different fluids.
117(2002); http://dx.doi.org/10.1063/1.1503309View Description Hide Description
A quantum dynamics study of a polyatomic combustionreaction accurately considering all its internal degrees of freedom is presented. The thermal rate constants for the reaction is calculated and compared to experimental and approximate theoretical results. Good agreement with experiment is found and the reliability of some of the approximate approaches is confirmed.
Methyl group rotational tunneling splittings and spin conversion dynamics: p-chlorotoluene in cyclohexane117(2002); http://dx.doi.org/10.1063/1.1504432View Description Hide Description
We performed spectralhole burning experiments in the UV with p-chlorotoluene as a probe in cyclohexane. A method is presented which allows for the determination of the rotational tunneling splitting in and The respective values are and From these numbers the rotational barriers and the respective rotational eigenvalues can be determined. Based on these results the spin conversion dynamics is reinterpreted as being governed by Orbach processes.