# Microcanonical statistical study of ortho-para conversion in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} at very low energies

## Abstract

The ortho-para conversion of H{sub 3}{sup +} and H{sub 2} in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} in interstellar space is possible by scrambling the five protons via (H{sub 5}{sup +}){sup *} complex formation. The product distribution of the ortho-para conversion reaction can be given by ratios of cumulative reaction probabilities (CRP) calculated by microcanonical statistical theory with conservation of energy, motional angular momentum, nuclear spin, and parity. A statistical method to calculate the state-to-state reaction probabilities for given initial nuclear spin species, rotational states, and collision energies is developed using a simple semiclassical approximation of tunneling and above-barrier reflection. A new calculation method of branching ratios for given total nuclear spins and scrambling mechanisms is also developed. The anisotropic long-range electrostatic interaction potential of H{sub 2} in the Coulomb field of H{sub 3}{sup +} is taken into account using the first-order perturbation theory in forming the complex. The CRPs and the product distribution of the ortho-para conversion reaction at very low energies with reactants in their ground vibronic and lowest rotational states for given initial nuclear spin species are presented as a function of collision energy assuming complete proton scrambling or incomplete protonmore »

- Authors:

- Department of Chemistry, University of Chicago, Chicago, Illinois 60637 and James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States)

- Publication Date:

- OSTI Identifier:
- 20991209

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Chemical Physics; Journal Volume: 126; Journal Issue: 4; Other Information: DOI: 10.1063/1.2430711; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CONVERSION; HYDROGEN; HYDROGEN IONS 3 PLUS; ION-MOLECULE COLLISIONS; PARITY; PERTURBATION THEORY; PROTONS; REACTION KINETICS; ROTATIONAL STATES; SEMICLASSICAL APPROXIMATION; SPIN; STATISTICAL MODELS; TUNNEL EFFECT

### Citation Formats

```
Park, Kisam, and Light, John C.
```*Microcanonical statistical study of ortho-para conversion in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} at very low energies*. United States: N. p., 2007.
Web. doi:10.1063/1.2430711.

```
Park, Kisam, & Light, John C.
```*Microcanonical statistical study of ortho-para conversion in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} at very low energies*. United States. doi:10.1063/1.2430711.

```
Park, Kisam, and Light, John C. Sun .
"Microcanonical statistical study of ortho-para conversion in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} at very low energies". United States.
doi:10.1063/1.2430711.
```

```
@article{osti_20991209,
```

title = {Microcanonical statistical study of ortho-para conversion in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} at very low energies},

author = {Park, Kisam and Light, John C.},

abstractNote = {The ortho-para conversion of H{sub 3}{sup +} and H{sub 2} in the reaction H{sub 3}{sup +}+H{sub 2}{yields}(H{sub 5}{sup +}){sup *}{yields}H{sub 3}{sup +}+H{sub 2} in interstellar space is possible by scrambling the five protons via (H{sub 5}{sup +}){sup *} complex formation. The product distribution of the ortho-para conversion reaction can be given by ratios of cumulative reaction probabilities (CRP) calculated by microcanonical statistical theory with conservation of energy, motional angular momentum, nuclear spin, and parity. A statistical method to calculate the state-to-state reaction probabilities for given initial nuclear spin species, rotational states, and collision energies is developed using a simple semiclassical approximation of tunneling and above-barrier reflection. A new calculation method of branching ratios for given total nuclear spins and scrambling mechanisms is also developed. The anisotropic long-range electrostatic interaction potential of H{sub 2} in the Coulomb field of H{sub 3}{sup +} is taken into account using the first-order perturbation theory in forming the complex. The CRPs and the product distribution of the ortho-para conversion reaction at very low energies with reactants in their ground vibronic and lowest rotational states for given initial nuclear spin species are presented as a function of collision energy assuming complete proton scrambling or incomplete proton scrambling. The authors show that the product distribution at very low energies (or very low temperatures) differs substantially from the high energy (or high temperature) limit branching ratios.},

doi = {10.1063/1.2430711},

journal = {Journal of Chemical Physics},

number = 4,

volume = 126,

place = {United States},

year = {Sun Jan 28 00:00:00 EST 2007},

month = {Sun Jan 28 00:00:00 EST 2007}

}