Dr. Paul D. Burrow, Professor Emeritus
Physics & Astronomy
University of Nebraska - Lincoln
024 T. Jorgensen Hall
Lincoln, Nebraska 68588-0299
office: (402) 472-2419
This electron scattering group has focused its attention on gas phase studies of temporary negative ion formation and decay in complex molecules. These transient species, having lifetimes in the 10-12 to 10-15 second range, are formed when an impinging electron occupies a normally empty molecular orbital. Such “resonances” dominate many electron scattering processes at energies from 0 to 10 eV. In particular, the presence of an electron in an antibonding orbital weakens the bond strengths causing the molecule to deform during the lifetime of the “resonance”. Upon autodetachment of the electron, the molecule may be left in a vibrationally excited state. In fact, temporary negative ion states are very efficient at exciting vibrational motion.
Currently the group is examining the dissociative electron attachment (DEA) process, a second means by which temporary negative ions may decay. In this reaction, a fragment having a positive electron affinity may carry off the temporarily bound electron, forming a neutral free radical and a permanentanion. This process is particularly important in halogenated hydrocarbons, such as those used in plasma etching. The DEA cross section is extraordinarily sensitive to many molecular parameters that are quite difficult to calculate, and thus, there exist no theoretical cross sections in systems larger than diatomics. The dynamic range of these cross sections can be enormous. In the series of chloromethanes, for example, peak cross sections vary by more than a factor of 106 with increasing chlorination.
Current emphasis is on molecules of biological interest such as the DNA bases and amino acids.
Scheer, AM (Scheer, A. M.); Gallup, GA (Gallup, G. A.); Burrow, PD (Burrow, P. D.), Unoccupied orbital energies of 1,4-benzenedithiol and the HOMO-LUMO gap, CHEMICAL PHYSICS LETTERS, 466 (4-6): 131-135 Dec 4 2008
Burrow, PD (Burrow, Paul D.); Gallup, GA (Gallup, Gordon A.); Modelli, A (Modelli, Alberto), Are there pi* shape resonances in electron scattering from phosphate groups?, JOURNAL OF PHYSICAL CHEMISTRY A, 112 (17): 4106-4113 May 1 2008
Pshenichnyuk, SA (Pshenichnyuk, S. A.); Asfandiarov, NL (Asfandiarov, N. L.); Burrow, PD (Burrow, P. D.), A relation between energies of the shor-lived negative ion states and energies of unfilled molecular orbitals for a series of bromoalkanes, RUSSIAN CHEMICAL BULLETIN, 56 (6): 1268-1270 Jun 2007
Pshenichnyuk, SA (Pshenichnyuk, Stanislav A.); Gallup, GA (Gallup, Gordon A.); Burrow, PA (Burrow, Paul A.), Low-energy electron capture by 6-aza-2-thiothymine: Investigations by electron attachment and electron transmission spectroscopies, JOURNAL OF PHYSICAL CHEMISTRY A, 111 (46): 11837-11842 Nov 22 2007
Scheer, AM (Scheer, A. M.); Mozejko, P (Mozejko, P.); Gallup, GA (Gallup, G. A.); Burrow, PD (Burrow, P. D.), Total dissociative electron attachment cross sections of selected amino acids, JOURNAL OF CHEMICAL PHYSICS, 126 (17): Art. No. 174301 May 7 2007
Onanong, S (Onanong, Sathaporn); Comfort, SD (Comfort, Steve D.); Burrow, PD (Burrow, Paul D.); Shea, PJ (Shea, Patrick J.), Using gas-phase molecular descriptors to predict dechlorination rates of chloroalkanes by zerovalent iron, ENVIRONMENTAL SCIENCE & TECHNOLOGY, 41 (4): 1200-1205 Feb 15 2007
Burrow, PD (Burrow, P. D.); Gallup, GA (Gallup, G. A.), Remote bond breaking by interacting temporary anion states, JOURNAL OF CHEMICAL PHYSICS, 125 (15): Art. No. 154309 Oct 21 2006
A. M. Scheer, K. Aflatooni, G. A. Gallup and P. D. Burrow, “Bond Breaking and Temporary Anion States in Uracil and Halouracils: Implications for the DNA Bases”, Phys. Rev. Lett. 92, 068102 (2004).
J.P. Sullivan, P. D. Burrow, D.S. Newman, K. Bartschat, J.A. Michejda, R. Panajotovic, M. Moghbelalhossein, R.P. McEachran and S.J. Buckman, “An Experimental and Theoretical Study of Transient Negative Ions in Mg, Zn, Cd and Hg”, New Journal of Physics 5, 159 (2003).
K. Aflatooni, G. A. Gallup and P. D. Burrow, “Temporary Anion States of closo-Carboranes and Diethyl Carborane”, J. Phys. Chem. A 106, 4703 (2002).
Kayvan Aflatooni, Ph.D., 1998, Associate Prof., Fort Hays State University, Hays, KS.