Electron stimulated desorption of H− from thin films of thymine and uracil

We present measurements of low energy (0–38 eV) electron stimulated desorption of H− from room temperature thin films of pure thymine (T) and uracil (U), condensed on polycrystalline Pt, and describe in detail the experimental methods required for such studies. The nominal film thicknesses are estimated to range from 0.08 to 2.7 monolayers; sublimation of the films at 69 °C (T) and 82 °C (U) onto the room temperature Pt substrate leads to nonuniform film growth, i.e., volumetric clustering, particularly in the submonolayer regime. H− formation by electron impact occurs via dissociative electron attachment (DEA) to the molecules, and results in strong desorption peaks near 8.6 eV for either molecule, whereas above 12–13 eV nonresonant dipolar dissociation dominates the desorption yields. Comparison of the present condensed phase results with gas phase measurements suggests that the desorbing H− produced at the DEA peak are mainly the result of CH bond cleavage, while near the desorption threshold of about ...

[1]  A. F. Fuciarelli,et al.  Radiation damage in DNA : structure/function relationships at early times , 1996 .

[2]  M. Huels,et al.  Low-energy (5-25 eV) electron damage to homo-oligonucleotides. , 1999, Radiation research.

[3]  Thomas H. Lowry,et al.  Mechanism and Theory in Organic Chemistry , 1976 .

[4]  Sanche,et al.  Mechanisms of charge trapping at a dielectric surface: Resonance stabilization and dissociative attachment. , 1988, Physical review letters.

[5]  T. Goulet,et al.  Monte Carlo simulation of fast electron and proton tracks in liquid water -- I. physical and physicochemical aspects , 1998 .

[6]  M. Isaacson.  Interaction of 25 keV Electrons with the Nucleic Acid Bases, Adenine, Thymine, and Uracil. I. Outer Shell Excitation , 1972 .

[7]  L. Christophorou,et al.  Atomic and Molecular Radiation Physics , 1971 .

[8]  K. Smith.  Aging, Carcinogenesis, and Radiation Biology , 1976, Springer US.

[9]  Parenteau,et al.  Formation of anionic excitations in the rare-gas solids and their coupling to dissociative states of adsorbed molecules. , 1993, Physical review. B, Condensed matter.

[10]  D. T. Goodhead,et al.  Microdosimetry: An interdisciplinary approach , 1997 .

[11]  C. Sonntag,et al.  The chemical basis of radiation biology , 1987 .

[12]  L. Sanche,et al.  Absolute and effective cross-sections for low-energy electron-scattering processes within condensed matter , 1998, Radiation and environmental biophysics.

[13]  Ramaker,et al.  Image charge effects in electron stimulated desorption: O- from O2 condensed on Ar films grown on Pt. , 1987, Physical review letters.

[14]  L. Christophorou,et al.  in Electron - Molecule Interactions and their Applications , 1984 .

[15]  A. Schweig,et al.  Functional subunits in the nucleic acid bases uracil and thymine , 1975 .

[16]  Paul A. Rowntree,et al.  Anion yields produced by low-energy electron impact on condensed hydrocarbon films , 1991 .

[17]  T. Lawrence,et al.  Halogenated pyrimidine sensitization of low dose rate irradiation in human malignant glioma. , 1993, International journal of radiation oncology, biology, physics.

[18]  E. Illenberger,et al.  Dissociative electron attachment to gas-phase 5-bromouracil , 2000 .

[19]  M. Lepage,et al.  LOW-ENERGY ELECTRON DAMAGE TO CONDENSED-PHASE DEOXYRIBOSE ANALOGUES INVESTIGATED BY ELECTRON STIMULATED DESORPTION OF H- AND ELECTRON ENERGY LOSS SPEC TROSCOPY , 1999 .

[20]  Michaud,et al.  Kinetic-energy distributions of O- produced by dissociative electron attachment to physisorbed O2. , 1995, Physical review. A, Atomic, molecular, and optical physics.

[21]  T. Kawai,et al.  Low dimensional self-organization of DNA-base molecules on Cu(111) surfaces , 1997 .

[22]  M. Isaacson,et al.  Electron Energy Loss Spectra of the Nucleic Acid Bases , 1971, Nature.

[23]  M. Huels,et al.  Halogen anion formation in 5-halouracil films: X rays compared to subionization electrons. , 1999, Radiation research.

[24]  E. Illenberger,et al.  Resonant dissociation of DNA bases by subionization electrons , 1998 .

[25]  R. H. Schuler,et al.  Uracilyl radical production in the radiolysis of aqueous solutions of the 5- halouracils , 1973 .

[26]  L. Sanche,et al.  The 2Πg shape resonance of N2 near a metal surface and in rare gas solids , 1990 .

[27]  D. Hunting,et al.  Resonant formation of DNA strand breaks by low-energy (3 to 20 eV) electrons. , 2000, Science.

[28]  P. Cullis,et al.  Effects of ionizing radiation on deoxyribonucleic acid. Part 7. Electron capture at cytosine and thymine , 1992 .