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	John Krenos Professor Email B.A. 1967, Connecticut M.S. 1968, Ph.D. 1972, Yale
	Contact   Links Phone: (732) 445-3048 Fax: (732) 445-5312 Lab: Dept: (732) 445-2618 Office: WL-221/187A Mail: Chemistry & Chemical Biology, 610 Taylor Road, Piscataway, NJ 08854

Summary

We are studying collisions of metastable (electronically excited) neon, argon, krypton, and xenon atoms with water molecules in a molecular beam apparatus. The total quenching cross sections are measured by suitable monitor reactions that isolate individual electronic states of the metastable atoms, a new technique pioneered in our laboratory. The energy-dependent quenching cross section provides insight into the nature of the long-range forces between excited atoms and ground-state molecules. For reactions that produce luminescent products, we obtain the energy-dependent product formation cross sections as well. Comparison of the formation cross section with the total quenching value reveals details of the strength of the nonadiabatic interaction that gives rise to a specific energy transfer channel. The vibrational and rotational distribution of the fluorescing fragment is obtained by higher resolution spectral measurements. Geometric features of the excited potential energy surface on which the reaction occurs are inferred from the observed internal energy distribution.

A plot of the quenching cross section for Ar* colliding with water molecules vs. relative velocity is shown in the above figure.

Simple inverse power fits are given for each data set. For Ar*(J=2) at low velocities, the observed power (0.713) is close to that predicted by the orbiting model (0.667) based on a long-range r to the minus 6 potential. At high velocities, the cross sections flatten as seen by extrapolation of the low velocity fit. The J=0 cross sections are lower than J=2, which is very unusual. The J=0 state is higher in energy and normally more easily quenched. The nature of the long-range correlation of potential curves to the J=2 and J=0 states of Ar* with water may explain this behavior. The velocity range for J=0 is restricted because of a limitation in the monitor method for Ar*. The data were obtained by Don Mueller.

Absolute Quenching Cross Section for Collisions Between Ar(³P_2,0) and H₂O J. Chem. Phys. 89, 7031-7033 (1988) Stephen Novicki and John Krenos

Molecular Beam Study of the Ne*(3s³P_2,0) + O₂(X³Σg^-) Reaction: Absolute Quenching and O*(3p⁵P, 3p³P) Product Cross Sections J. Phys. Chem. 97, 2106-2112 (1993) Don Mueller and John Krenos

Molecular Beam Study of the Collisions of State-Monitored, Metastable Noble Gas Atoms with O₂(X³Σg^-) J. Chem. Phys. 106, 3135-3145 (1997) Dawn Rickey and John Krenos

Study Guide for Atkins and Jones’s Chemical Principles: The Quest for Insight W. H. Freeman and Company, New York, 1999, 450 pages John Krenos and Joseph Potenza

Book Review of Chemical Kinetics and Reaction Dynamics, by P. L. Houston J. Chem. Educ. 78, 1466 (2001) John Krenos

Study Guide for Atkins and Jones’s Chemical Principles: The Quest for Insight Second Edition, W. H. Freeman and Company, New York, 2001, 476 pages John Krenos and Joseph Potenza

Reaction of Metastable Ar*(³P₂) and Kr*(³P₂) Atoms with Water Vapor: Excitation Functions for Electronic Quenching Collisions J. Phys. Chem. B 106, 8142-8147 (2002) Don R. Mueller and John Krenos

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