Interaction potential for He/H2 including the region of the van der waals minimum

Tsapline, B.; Kutzelnigg, Werner

doi:10.1016/0009-2614(73)80243-x

Cited by 93 publications

(10 citation statements)

References 15 publications

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“…Many of the early He-H 2 surfaces were intended only to describe the He + H 2 van der Waals potential well and the outer (low-energy) part of the He-H 2 repulsive wall [10][11][12][13][14][15][16]18,19,23 , and were valid only for equilibrium H 2 molecules. However, several analytic He-H 2 surfaces were intended to be valid in the higher-energy interaction region.…”

Section: B Previous Surfacesmentioning

confidence: 99%

“…available ab initio potential energy surfaces for H 3 (molecule plus open-shell atom) [1][2][3][4][5] or H 4 (two molecules) [6][7][8][9] . Previous analytic He-H 2 surfaces [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] were based on only a few dozen ab initio energies, which provided highly inadequate coverage of all but a very restricted region in the conformation space of He-H 2 . This paper reports a greatly-expanded set of ab initio energies, and a greatly improved He-H 2 PES fitted to these energies.…”

Section: Introductionmentioning

confidence: 99%

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Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Boothroyd

Martín

Peterson

2003

The Journal of Chemical Physics

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The interaction potential energy surface (PES) of He-H 2 is of great importance for quantum chemistry, as the simplest test case for interactions between a molecule and a closed-shell atom. It is also required for a detailed understanding of certain astrophysical processes, namely collisional excitation and dissociation of H 2 in molecular clouds, at densities too low to be accessible experimentally. A new set of 23 703 ab initio energies was computed, for He-H 2 geometries where the interaction energy was expected to be nonnegligible. These have an estimated rms "random" error of ∼ 0.2 millihartree and a systematic error of ∼ 0.6 millihartree (0.4 kcal/mol). A new analytic He-H 2 PES, with 112 parameters, was fitted to 20 203 of these new ab initio energies (and to an additional 4862 points generated at large separations). This yielded an improvement by better than an order of magnitude in the fit to the interaction region, relative to the best previous surfaces (which were accurate only for near-equilibrium H 2 molecule sizes). This new PES has an rms error of 0.95 millihartree (0.60 kcal/mole) relative to the the 14 585 ab initio energies that lie below twice the H 2 dissociation energy, and 2.97 millihartree (1.87 kcal/mole) relative to the full set of 20 203 ab initio energies (the fitting procedure used a reduced weight for high energies, yielding a weighted rms error of 1.42 millihartree, i.e., 0.89 kcal/mole). These rms errors are comparable to the estimated error in the ab initio energies themselves; the conical intersection between the ground state and the first excited state is the largest source of error in the PES.

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Section: B Previous Surfacesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Boothroyd

Martín

Peterson

2003

The Journal of Chemical Physics

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“…The calculations of Eastes & Secrest (1972), McGuire & Kouri (1974), and Alexander & McGuire (1976) used an interaction potential which neglected the van der Waals well. Tsapline & Kutzelnigg (1973) performed ab initio calculations of the HeH 2 potential energy surface (PES) which was extended with an analytic form by Raczkowski & Lester (1977) and made use of by Alexander (1977) and Raczkowski et al (1978) for extensive quantum scattering calculations. Recently, Muchnick & Russek (1994) provided a PES for the inter-HeÈH 2 action which included more recent ab initio potential energy calculations by Meyer et al (1980).…”

Section: Introductionmentioning

confidence: 99%

Quantum‐mechanical Study of Ro‐vibrational Transitions in H \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\

Balakrishnan

Forrey

Dalgarno

1999

ApJ

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We describe quantum-mechanical scattering calculations of ro-vibrational transitions in induced by H 2 collisions with He. We use a close-coupled description of the dynamics which includes full ro-vibrational coupling and a reliable potential energy surface. Rate coefficients for rotational and vibrational transitions in ortho-and are presented in the temperature range 10 ¹ T ¹ 5000 K. para-H 2 Subject headings : molecular data È molecular processes

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“…[1][2][3] The interaction potential energy surface ͑PES͒ involved in H 2 : He collisions is also relevant in quantum chemistry as the simplest interaction case between a molecule and a closed-shell atom. Therefore, many PESs have been proposed for this system, either on theoretical [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] or experimental basis. 19,20 Since the quality of the state-to-state cross sections and rate coefficients obtained from quantum scattering calculations strongly depends on the potential energy surface employed, experimental validation of these quantities indirectly implies the validation of the PES.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature inelastic collisions between hydrogen molecules and helium atoms

Tejeda

Thibault

Fernández

et al. 2008

The Journal of Chemical Physics

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Inelastic H(2):He collisions are studied from the experimental and theoretical points of view between 22 and 180 K. State-to-state cross sections and rates are calculated at the converged close-coupling level employing recent potential energy surfaces (PES): The MR-PES [J. Chem. Phys. 100, 4336 (1994)], and the MMR-PES and BMP-PESs [J. Chem. Phys. 119, 3187 (2003)]. The fundamental rates k(2-->0) and k(3-->1) for H(2):He collisions are assessed experimentally on the basis of a master equation describing the time evolution of rotational populations of H(2) in the vibrational ground state. These populations are measured in the paraxial region of supersonic jets of H(2)+He mixtures by means of high-sensitivity and high spatial resolution Raman spectroscopy. Good agreement between theory and experiment is found for the k(2-->0) rate derived from the MR-PES, but not for the BMP-PES. For the k(3-->1) rate, which is about one-third to one-half of k(2-->0), the result is less conclusive. The experimental k(3-->1) rate is compatible within experimental error with the values calculated from both PESs. In spite of this uncertainty, the global consistence of experiment and theory in the framework of Boltzmann equation supports the MR-PES and MMR-PESs, and the set of gas-dynamic equations employed to describe the paraxial region of the jet at a molecular level.

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Interaction potential for He/H2 including the region of the van der waals minimum

Cited by 93 publications

References 15 publications

Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Low-temperature inelastic collisions between hydrogen molecules and helium atoms

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