### Abstract

A general, full-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is further developed. The resulting computer program may be run in serial and parallel modes and is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the isomerizing acetylene/vinylidene system is presented. Large-scale calculations using a coordinate system based on orthogonal satellite vectors have been performed in six dimensions and vibrational term values and wave functions for acetylene and vinylidene states up to approximate to 23000 cm(-1) above the potential minimum have been determined. This has permitted the characterization of acetylene and vinylidene states at and above the isomerization barrier. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than in any variational calculations reported hitherto for this system. Comparison of the calculated density of states with that determined empirically suggests that our calculations are the most realistic achieved for this system to date. Indeed more states have been converged than in any previous study of this system. Calculations on lower lying excited states of acetylene based on HC - CH diatom-diatom coordinates give nearly identical results to those based on orthogonal satellite vectors. Comparisons are also made with calculations based on HH - CC diatom-diatom coordinates. (C) 2005 American Institute of Physics.

Original language | English |
---|---|

Number of pages | 9 |

Journal | The Journal of Chemical Physics |

Volume | 122 |

DOIs | |

Publication status | Published - 2005 |

### Keywords

- DIMENSIONALITY QUANTUM CALCULATIONS
- ACETYLENE/VINYLIDENE ISOMERIZATION
- SPECTROSCOPY
- HAMILTONIANS
- (C2H2)-C-12
- SURFACE

### Cite this

*The Journal of Chemical Physics*,

*122*. https://doi.org/10.1063/1.1850471

**Calculating energy levels of isomerizing tetra-atomic molecules. II. The vibrational states of acetylene and vinylidene.** / Kozin, I N ; Law, M M ; Tennyson, J ; Hutson, J M .

Research output: Contribution to journal › Article

*The Journal of Chemical Physics*, vol. 122. https://doi.org/10.1063/1.1850471

}

TY - JOUR

T1 - Calculating energy levels of isomerizing tetra-atomic molecules. II. The vibrational states of acetylene and vinylidene

AU - Kozin, I N

AU - Law, M M

AU - Tennyson, J

AU - Hutson, J M

PY - 2005

Y1 - 2005

N2 - A general, full-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is further developed. The resulting computer program may be run in serial and parallel modes and is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the isomerizing acetylene/vinylidene system is presented. Large-scale calculations using a coordinate system based on orthogonal satellite vectors have been performed in six dimensions and vibrational term values and wave functions for acetylene and vinylidene states up to approximate to 23000 cm(-1) above the potential minimum have been determined. This has permitted the characterization of acetylene and vinylidene states at and above the isomerization barrier. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than in any variational calculations reported hitherto for this system. Comparison of the calculated density of states with that determined empirically suggests that our calculations are the most realistic achieved for this system to date. Indeed more states have been converged than in any previous study of this system. Calculations on lower lying excited states of acetylene based on HC - CH diatom-diatom coordinates give nearly identical results to those based on orthogonal satellite vectors. Comparisons are also made with calculations based on HH - CC diatom-diatom coordinates. (C) 2005 American Institute of Physics.

AB - A general, full-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is further developed. The resulting computer program may be run in serial and parallel modes and is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the isomerizing acetylene/vinylidene system is presented. Large-scale calculations using a coordinate system based on orthogonal satellite vectors have been performed in six dimensions and vibrational term values and wave functions for acetylene and vinylidene states up to approximate to 23000 cm(-1) above the potential minimum have been determined. This has permitted the characterization of acetylene and vinylidene states at and above the isomerization barrier. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than in any variational calculations reported hitherto for this system. Comparison of the calculated density of states with that determined empirically suggests that our calculations are the most realistic achieved for this system to date. Indeed more states have been converged than in any previous study of this system. Calculations on lower lying excited states of acetylene based on HC - CH diatom-diatom coordinates give nearly identical results to those based on orthogonal satellite vectors. Comparisons are also made with calculations based on HH - CC diatom-diatom coordinates. (C) 2005 American Institute of Physics.

KW - DIMENSIONALITY QUANTUM CALCULATIONS

KW - ACETYLENE/VINYLIDENE ISOMERIZATION

KW - SPECTROSCOPY

KW - HAMILTONIANS

KW - (C2H2)-C-12

KW - SURFACE

U2 - 10.1063/1.1850471

DO - 10.1063/1.1850471

M3 - Article

VL - 122

JO - The Journal of Chemical Physics

JF - The Journal of Chemical Physics

SN - 0021-9606

ER -