Laser spectroscopic studies of the pure rotationalU0(0) andW0(0) transitions of solid parahydrogen

Solid Parahydrogen Infrared Matrix Isolation and Computational Studies of Lin-(C2H4)m Complexes

Complexes of lithium atoms with ethylene have been identified as potential hydrogen storage materials. As a Li atom approaches an ethylene molecule, two distinct low-lying electronic states are established; one is the ²A₁ electronic state (for C_2v geometries) that is repulsive but supports a shallow van der Waals well and correlates with the Li 2s atomic state, and the second is a ²B₂ electronic state that correlates with the Li 2p atomic orbital and is a strongly bound charge-transfer state. Only the ²B₂ charge-transfer state would be advantageous for hydrogen storage because the strong electric dipole created in the Li-(C₂H₄) complex due to charge transfer can bind molecular hydrogen through dipole-induced dipole and dipole-quadrupole electrostatic interactions. Ab initio studies have produced conflicting results for which electronic state is the true ground state for the Li-(C₂H₄) complex. The most accurate ab initio calculations indicate that the ²A₁ van der Waals state is slightly more stable. In contrast, argon matrix isolation experiments have clearly identified the Li-(C₂H₄) complex exists in the ²B₂ state. Some have suggested that argon matrix effects shift the equilibrium toward the ²B₂ state. We report the low-temperature synthesis and IR characterization of Li_n-(C₂H₄)_m (n = 1, m = 1 and 2) complexes in solid parahydrogen which are observed using the C═C stretching vibration of ethylene in the complex. These results show that under cryogenic hydrogen storage conditions the Li-(C₂H₄) complex is more stable in the ²B₂ electronic state and thus constitutes a potential hydrogen storage material with desirable characteristics.

Multiplet splittings and intensities of fine structure components of the Q1(0)H2 + S0(0)N2 transition in a solid parahydrogen matrix

A comprehensive analysis of theoretical multiplet splittings and intensities of the fine structure components of the Q(1)(0)H(2) + S(0)(0)N(2) transition in a solid parahydrogen crystal is presented. The consideration of higher order anisotropic term responsible for splittings is essential to explain the observed splitting of the three components. The pair interaction parameters DeltaB and DeltaC have been determined by comparing the theoretical splittings with the experimental values. The information about the small splittings (approximately 0.1 cm(-1)) due to crystal-field interaction is completely obscured due to fast hopping of v(') = 1, J(') = 0 H(2) vibron. Also, the theoretical expressions are derived for the intensities of the fine structure components of the Q(v(H(2)))(0) + S(v(N(2)))(0) transition and the theoretical results are compared with the experimental findings.