Temperature dependence of the hyperfine coupling constant of the D3O radical:: a direct ab initio molecular dynamics (MD) study

Temperature dependence of hyperfine coupling constants (hfcc's) of the D3O and H3O radicals, which are the important intermediates in interstellar molecular clouds, has been investigated by means of direct ab initio molecular dynamics (MD) method. The umbrella-bending mode of the D3O radical was activated by thermal energy, although the bending structure of the D3O radical did not inverse even at 300 K. From the MD calculations, it was predicted that deuterium- and hydrogen-hfcc (D- and H-hfcc) of D3O (H3O) increases with increasing temperature, whereas oxygen-hfcc decreases as temperature is increased. The effect of thermal activation on structure and electronic states of D3O (H3O) was discussed on the basis of theoretical results. (C) 2002 Elsevier Science B.V. All rights reserved.