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Title: Two-center interference in fast proton-H{sub 2}-electron transfer and excitation processes

Abstract

We present experimental evidence for a strong dependence on the angle between the molecular axis of H{sub 2} and the direction of the incoming projectile (p) in the cross section for transfer excitation in fast p-H{sub 2} collisions. For collision energies of 1.0 and 1.3 MeV we find good agreement between the observed data and an analytical expression based on a two-atomic-center description using Brinkman-Kramers amplitudes. This clearly shows that the observed angular dependence is a result of quantum mechanical interference and not a trivial geometrical effect.

Authors:
; ; ; ; ; ;  [1];  [2];  [1];  [3];  [4]; ;  [5];  [6]
  1. Department of Physics, Stockholm University, 10691 Stockholm (Sweden)
  2. Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)
  3. (Russian Federation)
  4. Fock Institute of Physics, St.Petersburg State University, 198504 St.Petersburg (Russian Federation)
  5. Manne Siegbahn Laboratory, S-104 05, Stockholm (Sweden)
  6. Angstroem Laboratory, Uppsala University, S-75121 Uppsala (Sweden)
Publication Date:
OSTI Identifier:
20786423
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 72; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.72.050703; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; AMPLITUDES; CATIONS; CHARGE EXCHANGE; ELECTRON TRANSFER; EXCITATION; HYDROGEN; HYDROGEN IONS; INTERFERENCE; ION-MOLECULE COLLISIONS; MEV RANGE; MOLECULES; PROTONS; QUANTUM MECHANICS

Citation Formats

Stoechkel, K., Eidem, O., Cederquist, H., Zettergren, H., Reinhed, P., Schuch, R., Schmidt, H. T., Cocke, C. L., Levin, S. B., Fock Institute of Physics, St.Petersburg State University, 198504 St.Petersburg, Ostrovsky, V. N., Kaelberg, A., Simonsson, A., and Jensen, J.. Two-center interference in fast proton-H{sub 2}-electron transfer and excitation processes. United States: N. p., 2005. Web. doi:10.1103/PHYSREVA.72.0.
Stoechkel, K., Eidem, O., Cederquist, H., Zettergren, H., Reinhed, P., Schuch, R., Schmidt, H. T., Cocke, C. L., Levin, S. B., Fock Institute of Physics, St.Petersburg State University, 198504 St.Petersburg, Ostrovsky, V. N., Kaelberg, A., Simonsson, A., & Jensen, J.. Two-center interference in fast proton-H{sub 2}-electron transfer and excitation processes. United States. doi:10.1103/PHYSREVA.72.0.
Stoechkel, K., Eidem, O., Cederquist, H., Zettergren, H., Reinhed, P., Schuch, R., Schmidt, H. T., Cocke, C. L., Levin, S. B., Fock Institute of Physics, St.Petersburg State University, 198504 St.Petersburg, Ostrovsky, V. N., Kaelberg, A., Simonsson, A., and Jensen, J.. Tue . "Two-center interference in fast proton-H{sub 2}-electron transfer and excitation processes". United States. doi:10.1103/PHYSREVA.72.0.
@article{osti_20786423,
title = {Two-center interference in fast proton-H{sub 2}-electron transfer and excitation processes},
author = {Stoechkel, K. and Eidem, O. and Cederquist, H. and Zettergren, H. and Reinhed, P. and Schuch, R. and Schmidt, H. T. and Cocke, C. L. and Levin, S. B. and Fock Institute of Physics, St.Petersburg State University, 198504 St.Petersburg and Ostrovsky, V. N. and Kaelberg, A. and Simonsson, A. and Jensen, J.},
abstractNote = {We present experimental evidence for a strong dependence on the angle between the molecular axis of H{sub 2} and the direction of the incoming projectile (p) in the cross section for transfer excitation in fast p-H{sub 2} collisions. For collision energies of 1.0 and 1.3 MeV we find good agreement between the observed data and an analytical expression based on a two-atomic-center description using Brinkman-Kramers amplitudes. This clearly shows that the observed angular dependence is a result of quantum mechanical interference and not a trivial geometrical effect.},
doi = {10.1103/PHYSREVA.72.0},
journal = {Physical Review. A},
number = 5,
volume = 72,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
  • Measurements on dissociative ionization of H{sub 2} and D{sub 2} by fast (16{endash}25 MeV) protons are carried out in an effort to understand two-electron processes in collisional ionization. The high velocity limit of the ratio of cross sections, {ital R}, of two-electron processes to one-electron processes obtained from these measurements along with earlier data is used to obtain a universal scaling law for {ital R} as a function of projectile charge and energy, irrespective of the sign of the projectile charge. {copyright} {ital 1996 The American Physical Society.}
  • The differential cross section of the dissociative ionization of H{sub 2}{sup +} by fast (2-keV) electron impact is determined theoretically using a two-center continuum wave function for the slow (50-eV) ejected electron satisfying the correct boundary conditions. The variation of the sevenfold differential cross section with the scattering angle for fixed molecular alignment shows diffraction patterns, which differ from those obtained by the multicenter atomic model of Messiah. The effect of the molecular alignment is studied for small, intermediate, and large scattering angles. This reveals preferential directions for the internuclear axis. {copyright} {ital 1996 The American Physical Society.}
  • The cross sections for the double ionization, ionization plus excitation, and double excitation of H{sub 2} by electrons and protons in the range of 350 to 3500 keV/amu have been measured. In all cases, the cross section for electron bombardment was greater than that for equivelocity proton bombardment. The results are discussed in terms of first and second Born processes and interferences between the two.
  • Solvent isotope effect studies of the proton-coupled electron transfer between the (Ru(bpy)/sub 2/(py)OH/sub 2/)/sup 2 +/ (I) and the oxidized forms (Ru(bpy)/sub 2/(py)OH)/sup 2 +/ and (Ru(bpy)(py)O)/sup 2 +/ are reported. A profound effect upon the rate constant for the oxidation of I resulting from substitution of D/sub 2/O for H/sub 2/O appears to be kinetic in origin. Electron-transfer rate constant showed a linear dependence on mole fraction of D/sub 2/O. (BLM)
  • Luminescence in the 200-580 nm spectral region was observed in the collisions of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} with CO in the 50-1000 eV projectile energy range. Using computer simulations, we have identified emission of the following products in the observed spectra: the CO{sup +}(A-X) comet-tail system, CO{sup +}(B-X) first negative system, CO{sup +}(B-A) Baldet-Johnson system, and CO(b-a) third positive system. Also, an emission from atomic hydrogen (H{sub β} line at 486nm) has been observed. From the analysis of the experimental spectra, we have determined the absolute emission cross-sections for the formation of the observed products.more » Computer simulations gave the excited-product population distributions over vibrational and rotational energy levels. The vibrational level distribution from the CO{sup +}(A-X) comet-tail system is compared with the data for CO excited by 100 eV electrons and extreme ultraviolet radiation (XUV) photons. We have used these data to analyze the excitation conditions in the comet Humason (1961e). From the vibrational population distributions observed in the comet, we found that this distribution can be reproduced if electrons produce 25%, protons 70%, and XUV photons produce 5% of the emitting molecules. We find that the ratio of the CO{sup +}(B-X) emission to the sum of two main emissions (CO{sup +}(A-X)+CO{sup +}(B-X)) is velocity dependent and does not depend on the projectile ion type. For small velocities (below 100 km s{sup –1}) the ratio is about 5%, while for higher velocities it increases to 30%. For these data, we have found an empirical formula that satisfactorily describes the experimental data: R = R {sub max}(1 – v {sub th}/v), (where R {sub max} = 33%, v {sub th} = 87 km s{sup –1}). This could be used to infer the velocity of ions producing the observed emission of CO{sup +} products.« less