Two-laser, action spectroscopy experiments have been performed in the I2B-X, ν′-0 spectral region on H 2•••I2 and D2••• I2 complexes to investigate the dependence of the H 2/D2 + I2 intermolecular interactions on orientation. The spectra contain features associated with at least two different conformers of the ground-state H2/D2••• I2(X,ν′′ = 0) complexes; one conformer has a preferred T-shaped geometry with the H2/D2 moiety localized in a potential minimum that is orthogonal to the I-I bond axis, and the second conformer has a linear geometry with the H2/D2 moiety positioned in minima at either end of the I2 molecule, along the bond axis. Those features associated with complexes containing para-H2(j = 0), ortho-H2(j = 1), ortho-D2(j = 0), and para-D 2(j = 1) are also assigned. The linear conformers are found to be more strongly bound than the T-shaped conformers with binding energies of 118.9(1.9) cm-1 versus 91.3-93.3 cm-1 for the ortho-H 2•••I2 complexes and 144.2(2.1) cm -1 versus 107.9 cm-1 for the para-D2• ••I2 complexes, respectively. Electronic structure calculations of the complexes containing ICl and I2 with H 2, He, Ne, and Ar were performed to reveal the nature of the interactions and to shed insight into the origins of the different binding energies. The most stable minima in the H2/D2 + I 2(B,ν′) excited-state potentials have T-shaped geometries. Calculated energies and probability amplitudes of the excited-state levels provide insight into the different excited-state intermolecular vibrational levels accessed by transitions of the two ground-state conformers.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry