Biomedical subjects

Robert J Le Roy

Publications and source records attributed to Robert J Le Roy.

4 recordsLinked to original sources

PubMed2006

An accurate analytic potential function for ground-state N2 from a direct-potential-fit analysis of spectroscopic data.

Two types of combined-isotopologue analysis have been performed on an extensive spectroscopic data set for ground-state N2 involving levels up to v=19, which is bound by half the well depth. Both a conventional Dunham-type analysis and a direct-potential-fit (DPF) analysis represent the data within (on average) the estimated experimental uncertainties. However, the Dunham-type parameters do not yield realistic predictions outside the range of the data used in the analysis, while the potential function obtained from the DPF treatment yields quantum mechanical accuracy over the data region and realistic predictions of the energies and properties of unobserved higher vibrational levels. Our DPF analysis also introduces a compact new analytic potential function form which incorporates the two leading inverse-power terms in the long-range potential.

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PubMed2006

An accurate ab initio potential energy surface and calculated spectroscopic constants for BeH2, BeD2, and BeHD.

A three-dimensional potential energy surface for the ground electronic state of BeH(2) has been determined by three-dimensional spline interpolation over 6864 symmetry-unique ab initio points calculated at the icMRCI/aug-cc-pV5Z level and corrected for core-electron correlation computed at the MR-ACPF/cc-pCV5Z level. Calculated spectroscopic constants of BeH(2) and BeD(2) are in excellent agreement with recent experimental results: for 11 bands of BeH(2) and 5 bands of BeD(2) the root mean square (rms) band origin discrepancies were only 0.15(+/-0.09) and 0.46(+/-0.19) cm(-1), respectively, and the rms relative discrepancies in the inertial rotational constants (B([v])) were only 0.028% and 0.023%, respectively. Spectral constants for BeHD were predicted using the same potential surface. The effect of different interpolation methods on predicted potential function values and on the calculated level energies and spectroscopic constants has been examined.

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PubMed2005

Direct-potential-fit analysis of new infrared and UV/visible A 1Sigma+-X 1Sigma+ emission spectra of AgH and AgD.

New high-resolution infrared and UV/visible spectra of (107)AgH, (109)AgH, (107)AgD, and (109)AgD have been recorded with a Fourier transform spectrometer. The new line positions are combined with published microwave and older electronic A (1)Sigma(+)-X (1)Sigma(+) data and used, first in a decoupled analysis of the X state alone, and then in a global multi-isotopologue analysis which yields comprehensive descriptions of both the X (1)Sigma(+) and A (1)Sigma(+) states of all four isotopologues of AgH. While the A state was long believed to be heavily perturbed, it is shown that its irregular spectrum merely reflects an unusual potential function shape. A direct fit of all data to appropriate radial Hamiltonians yields analytic potential-energy functions and Born-Oppenheimer breakdown radial functions for the ground X (1)Sigma(+) and A (1)Sigma(+) states.

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PubMed2005

A reliable new three-dimensional potential energy surface for H(2)-Kr.

An improved three-dimensional potential energy surface for the H(2)-Kr system is determined from a direct fit of new infrared spectroscopic data for H(2)-Kr and D(2)-Kr to a potential energy function form based on the exchange-Coulomb model for the intermolecular interaction energy. These fits require repetitive, highly accurate simulations of the observed spectra, and both the strength of the potential energy anisotropy and the accuracy of the new data make the "secular equation perturbation theory" method used in previous analyses of H(2)-(rare gas) spectra inadequate for the present work. To address this problem, an extended version of the "iterative secular equation" method was developed which implements direct Hellmann-Feynman theorem calculation of the partial derivatives of eigenvalues with respect to parameters of the Hamiltonian which are required for the fits.

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