ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Several variational methods are applied to the calculation of the position and width of the lowest 1S resonance state of H−, which is the simplest physical example of an electronic Feshbach resonance. These methods include two different versions of the analytic continuation of stabilization graphs that enforce the correct branch-point structure and two versions of the complex-stabilization approach, one that stabilizes the complex resonance energy with respect to the exponents of the complex orbital(s) and one that stabilizes it with respect to both the real and complex orbital exponents. The calculations involve medium-, large-, and very-large-sized basis sets of Gaussian orbitals and full configuration interaction (CI). The use of the same basis sets with the various methods allows for detailed comparisons among them. Although the sensitivity of the results to the fit parameters prevents true convergence, reliable estimates of the position and width of this resonance (about four-figure accuracy in the position and two-figure accuracy in the width) are obtained both from a version of the analytic continuation of stabilization graphs that employs one eigenvalue of a real, Hermitian Hamiltonian matrix but enforces the correct branch-point structure and from a complex-stabilization approach that involves complex basis functions and a non-Hermitian Hamiltonian matrix. In the former approach, we find that the results are less accurate when two eigenvalues of the Hamiltonian matrix are employed in the analytic continuation, possibly due to interactions with excited resonance states. For the latter approach, we show that good results can be obtained with basis sets containing a single complex orbital if the resonance energy is also stabilized with respect to an analytic continuation of the real orbital exponents, but that there is no advantage in using two complex orbitals with close exponents.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.460354
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