skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Validity of the isolated resonance picture for H{sub 2} autoionizing states

Abstract

The isolated resonance picture (IRP) is tested by comparing calculations on doubly excited autoionizing states of H{sub 2} by using two different theoretical approaches: a recent implementation of the exterior complex scaling method and the standard Feshbach method with B-spline basis sets. These calculations demonstrate that the IRP can yield poor approximations to autoionization widths when doubly excited states approach the ionization threshold at large internuclear distances, R. In contrast, at small R where avoided crossings appear, the IRP produces accurate resonance parameters.

Authors:
;  [1];  [2];  [3]
  1. Departamento de Quimica C-IX, Universidad Autonoma de Madrid, 28049-Madrid (Spain)
  2. Departments of Applied Science and Chemistry, University of California, Davis, California 95616 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
20786805
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevA.73.014702; (c) 2006 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; APPROXIMATIONS; AUTOIONIZATION; DISTANCE; EXCITED STATES; HYDROGEN; MOLECULES; RESONANCE

Citation Formats

Morales, Felipe, Martin, Fernando, McCurdy, C. William, and Lawrence Berkeley National Laboratory, Chemical Sciences, Berkeley, California 94720. Validity of the isolated resonance picture for H{sub 2} autoionizing states. United States: N. p., 2006. Web. doi:10.1103/PHYSREVA.73.0.
Morales, Felipe, Martin, Fernando, McCurdy, C. William, & Lawrence Berkeley National Laboratory, Chemical Sciences, Berkeley, California 94720. Validity of the isolated resonance picture for H{sub 2} autoionizing states. United States. doi:10.1103/PHYSREVA.73.0.
Morales, Felipe, Martin, Fernando, McCurdy, C. William, and Lawrence Berkeley National Laboratory, Chemical Sciences, Berkeley, California 94720. Sun . "Validity of the isolated resonance picture for H{sub 2} autoionizing states". United States. doi:10.1103/PHYSREVA.73.0.
@article{osti_20786805,
title = {Validity of the isolated resonance picture for H{sub 2} autoionizing states},
author = {Morales, Felipe and Martin, Fernando and McCurdy, C. William and Lawrence Berkeley National Laboratory, Chemical Sciences, Berkeley, California 94720},
abstractNote = {The isolated resonance picture (IRP) is tested by comparing calculations on doubly excited autoionizing states of H{sub 2} by using two different theoretical approaches: a recent implementation of the exterior complex scaling method and the standard Feshbach method with B-spline basis sets. These calculations demonstrate that the IRP can yield poor approximations to autoionization widths when doubly excited states approach the ionization threshold at large internuclear distances, R. In contrast, at small R where avoided crossings appear, the IRP produces accurate resonance parameters.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 1,
volume = 73,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • A new three-photon double-resonance excitation scheme for H/sub 2/ is combined with time-of-flight ion detection and is used for high-resolution spectroscopy of autoionizing and field-ionizing Rydberg states. Using modest laser powers, we have achieved a Doppler-limited resolution of 0.15 cm/sup -1/.
  • A numerical investigation of the doubly excited states of H{sub 2} converging to the H(n=2)+H(n{sup '}=2) limit was performed. Special emphasis was put on the accurate description of the range of intermediate internuclear distances in order to correctly connect the short range with the asymptotic van der Waals regime where perturbation theory is applicable. The present nonperturbative calculation extends to internuclear separations R=200a{sub 0} and is sufficiently accurate to achieve a connection between the two extreme regimes without any need for an interpolation procedure. The high precision of the ab initio results revealed a long range dipole-quadrupole interaction that hadmore » been omitted in two earlier calculations. In addition to revised first-order perturbation theory results the leading second-order term varying as R{sup -6} was obtained. The impact of the present findings for cold H(n=2) collisions is briefly discussed.« less
  • The complex-scaling method is applied to the study of molecular resonances within the framework of the Born-Oppenheimer approximation. In this procedure only the electronic coordinates of the Born-Oppenheimer Hamiltonian are scaled, and thus only the electron-nuclear attraction integrals need be recalculated with explicit complex arguments for each value of the scaling parameter. This method is applied to the study of resonances of H/sub 2/ and H/sub 2/ /sup -/. This represents the first successful application of a complex-scaling procedure to the study of a molecular resonance.
  • Double-resonance spectroscopy of N 2 via the a 1Π g, v´=5 level has enabled the definitive assignment of a number of intense and heretofore unidentified bands observed in the single-photon spectrum in the region between the X 2Σ g + v +=0 and 1 ionization thresholds. The results resolve several long-standing controversies concerning the assignment of Rydberg states of low principal quantum number that converge to the A 2Π u and B 2Σ u + states of the ion and indicate that significant revisions of previous assignments are necessary. The spectra are discussed in the context of the entire manifoldmore » of states in this region, which includes high vibrational levels of the b´ 1Σ u + valence state as well as Rydberg states that converge to the X 2Σ g +, A 2Π u, and B 2Σ u + states of the ion.« less