V. Chandrasekharan

Rydberg fluorescence of NO trapped in rare gas matrices

Fluorescence spectra from the Rydberg A 2Σ+ (v=0) level of NO trapped in Ne, Ar, Kr, and Xe matrices have been obtained for two different sites. The main site is characterized by broad A(0,v‘) bands (FWHM≂80 meV), blue gas‐to‐matrix shifts of 70 to 300 meV, and by absorption–emission Stokes shifts of 300 meV in Xe to 800 meV in Ne matrices. The line shapes and Stokes shifts are treated within a configuration coordinate model by a moment analysis. A linear and quadratic coupling is invoked with relaxation energies ranging for the excited state from 160 meV in Xe to 540 meV in Ne and for the ground state from 150 meV in Xe to 280 meV in Ne and an increase of the cage radius of 3% in Xe to 15% in Ne. The ‘‘red’’ site fluorescence shows emission bands with matrix shifts of −140 meV in Xe to 80 meV in Ne and absorption–emission Stokes shifts of 210 meV in Xe to 830 meV in Ne. Red site ‘‘hot’’ A (v=1) fluorescence is also observed. Red sites are attributed to local disorder around the molecule in Ar, Kr, and Xe...

Reinvestigation of the Raman spectra of dihydrogen trapped in rare gas solids. I. H2, HD, and D2 monomeric species

The vibration–rotation and pure rotational Raman spectra of H2, HD, and D2 trapped in Ar, Kr, and Xe matrices have been recorded at 9 K. The frequencies which have been measured within an accuracy of 0.3 cm−1 are compared to the results of recent calculations. Except for the S0(0) line of HD the agreement between observed and calculated matrix shifts is satisfactory. The anomalous blue shift observed for the S0(0) line of HD is well interpreted within the rotation translation coupling (RTC) framework.

Mechanisms of the L’ 2Φ–X 2Π emission of NO in Ar and Kr matrices

New time and energy resolved spectra of the L’ 2Φ–X 2Π (0,v″) bands of NO in Ar and Kr matrices are reported. The L’(0,v″) bands are excited exclusively via the B’ 2Δ valence state and their lifetime is 3000±500 ns in both matrices. The quantum efficiency for L’(v=0) emission is estimated to be ≤0.04. The 2Φ–2Π transition is discussed in terms of a statically induced transition moment involving spin–orbit mixing with B’ 2Δ, but also in terms of nonadiabatic matrix elements due to the coupling to the lattice. Relaxation down to L’(v=0) is discussed in terms of matrix‐induced interstate cascading with the b 4Σ− state.

Vibrationally hot rydberg luminescence of no in Ne matrices

Emission from the valence levels B2P (v = 3-5) of NO embedded in Ne crystals following excitation of the Rydberg level A 2S+ (v = 2) by synchrotron radiation is reported. A 2-step process combining bubble formation around the Rydberg state and Rydberg->valence energy transfer is invoked in order to account for these emissions. [on SciFinder (R)]

Vibrationally “hot” valence luminescence of NO in Ne matrices

Abstract Emission from the valence levels B2Π (v=3, 4 and 5) of NO embedded ion Nc crystals following excitation of the Rydberg level A2Σ+ (v=2) by synchroton radiation is reported. A two step process combining bubble formation around the Rydberg state and Rydberg→valence energy transfer is invoked in order to account for these emissions.

Modelling light diatomics trapped in rare gas matrices: H2, HD and D2 in Ar, Kr and Xe

The different models allowing the calculations of the rovibrational frequency shifts with respect to the free molecule of a molecular impurity embedded in a rare gas crystal are reviewed. It is shown that models which account for the translational motion of the impurity yield reliable results, the effects of the rare-gas translation seem to be less important. The different models currently used are described in detail and the computational procedures are discussed. Finally, it is shown that for heteronuclear diatomics, the translation-rotation coupling could play an important role.