Rate constants for the photodissociation of the <em>b</em> <sup>3</sup>Σ<sup>+</sup> state as a function of the temperature <em>T</em><sub>*</sub> of the blackbody, for different Maxwell–Boltzmann distribution temperatures <em>T</em><sub><em>M</em> − <em>B</em></sub>

<p><strong>Figure 8.</strong> Rate constants for the photodissociation of the <em>b</em> <sup>3</sup>Σ<sup>+</sup> state as a function of the temperature <em>T</em><sub>*</sub> of the blackbody, for different Maxwell–Boltzmann distribution temperatures <em>T</em><sub><em>M</em> − <em>B</em></sub>. The <em>T<sub>MB</sub></em> = 2 result, for which only the <em>v</em>'' = 0, <em>J</em>'' = 0 level is populated, is obtained for all Maxwell–Boltzmann distribution temperatures if the vibrational dependence of the cross section is neglected, as the photodissociation cross sections for all <em>v</em>'', <em>J</em>'' levels are then assumed to be equal to the cross section for the <em>v</em>'' = 0, <em>J</em>'' = 0'' level.</p> <p><strong>Abstract</strong></p> <p>We illustrate some of the difficulties that may be encountered when computing photodissociation and radiative association cross sections from the same time-dependent approach based on wavepacket propagation. The total and partial photodissociation cross sections from the 33 vibrational levels of the <em>b</em> <sup>3</sup>Σ<sup>+</sup> state of HeH<sup>+</sup> towards the nine other <sup>3</sup>Σ<sup>+</sup> and 6 <sup>3</sup>Π <em>n</em> = 2, 3 higher lying electronic states are calculated, using the autocorrelation method introduced by Heller (1978 <em>J. Chem. Phys.</em> <strong>68</strong> 3891) and the method based on the asymptotic behaviour of wavepackets introduced by Balint-Kurti <em>et al</em> (1990 <em>J. Chem. Soc. Faraday Trans.</em> <strong>86</strong> 1741). The corresponding radiative association cross sections are extracted from the same calculations, and the photodissociation and radiative association rate constants are determined.</p>