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Studies of multichannel rotational predissociation of Ar–H2 van der Waals molecule by the complex-coordinate coupled-channel formalism

J. Chem. Phys. 76, 5307 (1982); doi:10.1063/1.442929

Issue Date: 1 June 1982

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Shih-I Chu and Krishna K. Datta
Department of Chemistry, University of Kansas, Lawrence, Kansas 66045
The complex-coordinate coupled-channel (CCCC) formalism previously developed [J. Chem. Phys. 72, 4772 (1980)] is applied to the accurate determination of the level widths (lifetimes) and energies of rotationally predissociating metastable Ar···H2 van der Waals molecules. Calculations are performed using several realistic anisotropic potentials obtained recently by experiments, including Lennard-Jones (LJ), Buckingham–Corner (BC) type potentials, as well as the semiempirical potential of Tang–Toennies (TT). New numerical methods are introduced here to deal with the complex rotations of piecewise inhomogeneous potentials such as those of BC and TT. It is found that the CCCC method is capable of providing reliable results for any given potential surface. Furthermore, the CCCC results are sensitive to the potential surfaces used. For example, the linewidths predicted for different LJ potential surfaces considered here vary by a factor as large as 4. However, the agreement among more recent potentials, namely, the BC potential of Zandee and Reuss and that of Le Roy and Carley as well as the potential of Tang and Toennies, is much closer: the resonance energies agree to within 1 cm−1 and the linewidths to within 30%. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.
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KEYWORDS and PACS

Keywords
PACS
  • 34.20.Fi
    Atomic and molecular collision processes and interactions Interatomic and intermolecular potentials and forces Long-range forces
  • 33.80.Gj
    Molecular spectra and interactions of molecules with photons Molecular photon processes Diffuse spectra; predissociation, photodissociation
  • 33.70.Jg
    Molecular spectra and interactions of molecules with photons Intensities and shapes of molecular spectral lines and bands Line and band widths, shapes, and shifts
  • YEAR: 1982

PUBLICATION DATA

ISSN:
0021-9606 (print)   1089-7690 (online)
Publisher:
AIP is a member of CrossRef AIP

REFERENCES (34)
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  1. For a recent review, see R. J. Le Roy and J. S. Carley, Adv. Chem. Phys. 42, 353 (1980).
  2. For recent reviews, see (a) J. Reuss, Adv. Chem. Phys. 30, 389 (1976);
  3. (b) K. Thuis, S. Stolte, and J. Reuss, Comments At. Mol. Phys. 8, 123 (1979).
  4. (a) L. Zandee and J. Reuss, Chem. Phys. 26, 327 (1977);
  5. (b) 26, 345 (1977).
  6. (a) R. J. Le Roy and J. van Kranendonk, J. Chem. Phys. 61, 4750 (1974);
    7. (b) R. J. Le Roy, J. S. Carley, and J. E. Grabenstetter, Faraday Discuss. Chem. Soc. 62, 169 (1977);
    (c) J. S. Carley, ibid. 62, 303 (1977);
    (d) J. S. Carley, Ph.D. thesis, University of Waterloo, Waterloo, Ontario, 1978.
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    9. and references cited therein; T. E. Gough, R. E. Miller, and G. Scoles, ibid. 69, 1588 (1978).
  9. J. E. Grabenstetter and R. J. Le Roy, Chem. Phys. 42, 41 (1979).
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  11. S.-I. Chu, J. Chem. Phys. 72, 4772 (1980).
  12. See, for example, Int. J. Quantum Chem. 14, No. 4 (1978).
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    14. (b) O. Atabek and R. Lefebvre, Chem. Phys. 55, 395 (1981).
  14. (a) K. T. Tang and J. P. Toennies, J. Chem. Phys. 66, 1496 (1977);
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    (c) 74, 1148 (1981).
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    Ann. Math. 97, 247 (1973).
  17. I. C. Percival and M. J. Seaton, Proc. Cambridge Philos. Soc. 53, 654 (1957).
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  21. Since only one complex eigenvalue is desired, the inverse iteration technique (see, for example, Ref. 20) was used, which reduced the amount of computer time substantially.
  22. S.-I. Chu, Chem. Phys. Lett. 54, 367 (1978).
  23. M. Waaijer, Ph.D. thesis, Katholieke University, Nijmegen, The Netherlands, 1981.
  24. A. M. Rulis, K. M. Smith, and G. Scoles, Can. J. Phys. 56, 753 (1978).
  25. The spurious widths associated with the unperturbed van der Waals vibrational bound states occur because the diagonal-block matrices such as <j = l = 2, n|Halpha|j[prime] = l[prime] = 2, n[prime]> are complex symmetric. In general, a smaller spurious width indicates a better quality of the bound state wave function. The (real) physical widths are induced by the off-diagonal coupling blocks.
  26. K. K. Datta and S.-I. Chu, Scaling, Chem. Phys. Lett. (in press).
  27. K. K. Datta and S.-I. Chu (to be published).
  28. S.-I. Chu and K. K. Datta (to be published).
  29. (a) B. Schneider, Chem. Phys. Lett. 31, 237 (1975);
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  31. The kinetic energy matrix elements are independent of the coordinate (X or R) used for complex rotation.
  32. S.-I Chu (unpublished results).
  33. The fact that the spurious widths of the BC and TT potentials do not decrease rapidly with N is probably mainly due to the inhomogeneity or piecewise nature of their analytic representations.
  34. The strength of the anisotropy is best measured by the magnitude of the anisotropic parameters such as q6 and q12 of LJ potentials in Table I. It is seen there that LJ(I) has the largest q6 and q12 values and, therefore, is the “strongest” anisotropic potential.
  35. Although the spread of the linewidths ([cyrillic GHE]) for the various potentials (Fig. 9) are mainly caused by the differences among the anisotropic potentials, the spread of the resonance energies (ER) can be largely accounted for (within 90%) by the differences among the zero-order isotropic potentials.
  36. K. P. Huber and G. Herzberg, Molecular Spectra and Molecular Structure (Van Nostrand Reinhold, New York, 1979), Vol. IV.

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