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Papers by R. Levine

Research paper thumbnail of Vibrational enhancement of the reaction rate and steric requirements in the H+ D 2 (ν) and D+ H 2 (χ) reactions

Research paper thumbnail of Translational energy disposal in molecular collisions: The transfer of momentum constraint

Chemical Physics Letters, 1975

... The trajectory results for the CIiEJE reaction, fig. 3, vali date this expectation. ... Froc.... more ... The trajectory results for the CIiEJE reaction, fig. 3, vali date this expectation. ... Froc. Phys. 8cc. (London) 84 (1964) 527. [24] WR Gentry, EA. Gislason, BH Mahan and CW Tsao, J. Chem. Plays. 49 (1968) 3058. [25] KT Gillen, BH Malien and JS Winn, J. Chem. Plays. ...

Research paper thumbnail of Insertion vs. abstraction in the H+ H/sub 2/.-->. H/sub 2/+ H exchange reaction

Research paper thumbnail of Insertion vs. abstraction in the atomic hydrogen+ molecular hydrogen. fwdarw. molecular hydrogen+ atomic hydrogen exchange reaction

At collision energies above 1 eV an insertion mechanism is shown to dominate in the hydrogen exch... more At collision energies above 1 eV an insertion mechanism is shown to dominate in the hydrogen exchange reaction. The cone of acceptance for reaction is found to be made up of an inner cone (Le., for more nearly collinear collisions) where exchange proceeds by abstraction and an outer spherical sector where the mechanism is by insertion. The cross section for reaction, computed by classical trajectories, declines at energies above ca. 1 eV due to a recrossing of the transition state after a collision with an inner hard core. Thus, while the barrier to insertion is higher, this mechanism dominates for such hot H atoms as are currently available from photodissociation. For the H + HD reaction with rotationally cold HD, the cone of acceptance about the D atom is significantly wider.

Research paper thumbnail of Thermodynamic functions of molecular hydrogen from ab initio energy levels

Molecular Physics, 1974

A tabulation is presented of the thermodynamic properties of molecular hydrogen (H2, D2 and HD), ... more A tabulation is presented of the thermodynamic properties of molecular hydrogen (H2, D2 and HD), calculated using energy levels which had been obtained via a solution of the Schrödinger equation. The present results should be more accurate than prior computations based on spectroscopic extrapolation formulae. They provide the first example of an accurate determination of a bulk, macroscopic property directly from first principles (input: masses and Coulomb's law).The results are tabulated for ortho, para, the equilibrium and the frozen (or ‘normal’) mixture (3 : 1 for H2, 1 : 2 for D2) over the temperature range 5–300 K and for the frozen mixture up to 6000 K.The importance of anharmonicity and of quasi-bound levels at high temperatures is discussed.

Research paper thumbnail of The well-reasoned choice: An information-theoretic approach to branching ratios in molecular rate processes

Research paper thumbnail of Rotational excitation of interstellar OH molecules

The Astrophysical Journal, 1977

Research paper thumbnail of Quasi-bound states of coupled Morse oscillators

Chemical Physics Letters, 1985

Two different methods for approximating these as local&d states are compared. The algebraic appro... more Two different methods for approximating these as local&d states are compared. The algebraic approach is shown to be in very good accord with-the other method which is formulated in coordinate space and hence is differential in character. For these highly excited states an intennul~plet mixing term is included in the algebraic Hamiltoniau + For the technical def?nit%on of "compact" and other group theoretic terms. see ref. [ 131. 0 009-2614/85/Z% 03.30 0 Ekevier Science Publishers B-V.

Research paper thumbnail of ANALYSIS OF ELECTRONICALLY NONADIABATIC CHEMICAL REACTIONS: AN ENFORMATION THEORETIC APPROACH

A practical procedure for tie determination of branching ratios for reactions which lead to eithe... more A practical procedure for tie determination of branching ratios for reactions which lead to either excited or electronic& ly ground state products is outlined. The method is applied to four reactions which could (on energetic grounds) produce 231 electroni&ly excited iod;mZe atom. No2uSe of a complete inversion is Found, but &e reaction (F f HI) is pidictd to yieId a siatistical, (one hff), I ( PI/z) to I( P3/2) ratio.

Research paper thumbnail of Vibrational enhancement of the reaction rate and steric requirements in the H+ D 2 (ν) and D+ H 2 (χ) reactions

Research paper thumbnail of Translational energy disposal in molecular collisions: The transfer of momentum constraint

Chemical Physics Letters, 1975

... The trajectory results for the CIiEJE reaction, fig. 3, vali date this expectation. ... Froc.... more ... The trajectory results for the CIiEJE reaction, fig. 3, vali date this expectation. ... Froc. Phys. 8cc. (London) 84 (1964) 527. [24] WR Gentry, EA. Gislason, BH Mahan and CW Tsao, J. Chem. Plays. 49 (1968) 3058. [25] KT Gillen, BH Malien and JS Winn, J. Chem. Plays. ...

Research paper thumbnail of Insertion vs. abstraction in the H+ H/sub 2/.-->. H/sub 2/+ H exchange reaction

Research paper thumbnail of Insertion vs. abstraction in the atomic hydrogen+ molecular hydrogen. fwdarw. molecular hydrogen+ atomic hydrogen exchange reaction

At collision energies above 1 eV an insertion mechanism is shown to dominate in the hydrogen exch... more At collision energies above 1 eV an insertion mechanism is shown to dominate in the hydrogen exchange reaction. The cone of acceptance for reaction is found to be made up of an inner cone (Le., for more nearly collinear collisions) where exchange proceeds by abstraction and an outer spherical sector where the mechanism is by insertion. The cross section for reaction, computed by classical trajectories, declines at energies above ca. 1 eV due to a recrossing of the transition state after a collision with an inner hard core. Thus, while the barrier to insertion is higher, this mechanism dominates for such hot H atoms as are currently available from photodissociation. For the H + HD reaction with rotationally cold HD, the cone of acceptance about the D atom is significantly wider.

Research paper thumbnail of Thermodynamic functions of molecular hydrogen from ab initio energy levels

Molecular Physics, 1974

A tabulation is presented of the thermodynamic properties of molecular hydrogen (H2, D2 and HD), ... more A tabulation is presented of the thermodynamic properties of molecular hydrogen (H2, D2 and HD), calculated using energy levels which had been obtained via a solution of the Schrödinger equation. The present results should be more accurate than prior computations based on spectroscopic extrapolation formulae. They provide the first example of an accurate determination of a bulk, macroscopic property directly from first principles (input: masses and Coulomb's law).The results are tabulated for ortho, para, the equilibrium and the frozen (or ‘normal’) mixture (3 : 1 for H2, 1 : 2 for D2) over the temperature range 5–300 K and for the frozen mixture up to 6000 K.The importance of anharmonicity and of quasi-bound levels at high temperatures is discussed.

Research paper thumbnail of The well-reasoned choice: An information-theoretic approach to branching ratios in molecular rate processes

Research paper thumbnail of Rotational excitation of interstellar OH molecules

The Astrophysical Journal, 1977

Research paper thumbnail of Quasi-bound states of coupled Morse oscillators

Chemical Physics Letters, 1985

Two different methods for approximating these as local&d states are compared. The algebraic appro... more Two different methods for approximating these as local&d states are compared. The algebraic approach is shown to be in very good accord with-the other method which is formulated in coordinate space and hence is differential in character. For these highly excited states an intennul~plet mixing term is included in the algebraic Hamiltoniau + For the technical def?nit%on of "compact" and other group theoretic terms. see ref. [ 131. 0 009-2614/85/Z% 03.30 0 Ekevier Science Publishers B-V.

Research paper thumbnail of ANALYSIS OF ELECTRONICALLY NONADIABATIC CHEMICAL REACTIONS: AN ENFORMATION THEORETIC APPROACH

A practical procedure for tie determination of branching ratios for reactions which lead to eithe... more A practical procedure for tie determination of branching ratios for reactions which lead to either excited or electronic& ly ground state products is outlined. The method is applied to four reactions which could (on energetic grounds) produce 231 electroni&ly excited iod;mZe atom. No2uSe of a complete inversion is Found, but &e reaction (F f HI) is pidictd to yieId a siatistical, (one hff), I ( PI/z) to I( P3/2) ratio.

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