Millard Alexander's Research


Research in our group involves the theoretical study of molecular collisions, particularly those involving free radicals, the photofragmentation of small molecules, and the structure and energetics of weakly bound complexes involving open-shell species. Our interest is the coupling of the vibrational and rotational motion of the nuclei with the spin and orbital motion of the electrons. Of particular recent interest is a new quantum flux method for the study of the detailed mechanism of photofragmentation and energy transfer. Within the past several years we have developed a new code to treat, fully quantum mechanically, abstraction reactions involving multiple electronic potential energy surfaces.

Current investigations include:

a) The effect of spin-orbit coupling in the reaction of halogens (F and Cl) with hydrogen (for example: F+H2 → HF + H).

b) The effect of multiple potential energy surfaces in product branching in the reaction of O(3P) and S(3P) with H2 and in the quenching of OH(A2Σ) by H2.

c) The fully-quantum investigation of reaction and relaxation of the OH radical by collisions with O atoms.

d) The assignment of the bend-stretch levels of weakly bound complexes such as BH-Ar, CH-Ar, OH-Ne, NH-Ar, B-Ar, and B-H2.

e) The development of new methods for the determination of the structure and energetics of complexes involving an open-shell atom imbedded in noble gases or molecular hydrogen


Our work has been instrumental in interpreting experimental work done in the groups of Xueming Yang (Dalian, China) and Daniel Neumark (U. C. Berkeley). This work has been highlighted recently on the homepage of the College of Chemical and Life Sciences at the University of Maryland, in a perspective article in Science by Professor Joel Bowman of Emory University, in a general interest article in Chemistry World and another article in Chemical and Engineering News.
This work involves quantum scattering calculations using our Hibridon code for inelastic collisions, as well as, for reactive collisions, with our extension to multiple potential-energy surfaces of the ABC code of Manolopoulos, Skouteris and Castillo, and high precision ab initio determination of molecular potential energy surfaces using the MOLPRO code of Werner and Knowles. The calculations are done on Apple G5 and Intel Xeon workstations and servers in our own group as well as on the Deepthought cluster of Linux Xeon servers at the University of Maryland.

For the past 25 years our research group has had exceptionally close ties and joint funding with the experimental group of Paul Dagdigian at The Johns Hopkins University. In addition we have long-standing collaborative contacts with the theoretical groups of Hans-Joachim Werner at the University of Stuttgart (Germany) and David Manolopoulos at Oxford University (UK).