Journal of Molecular Spectroscopy最新文献

We report spectroscopic observation and theoretical calculations of a new isomer of (CS₂)₃ as observed in the regions of the ν₃ fundamental band of CS₂ (6.5 μm) and the ν₁ + ν₃ combination band (4.5 μm), using tunable laser sources and a pulsed supersonic slit-jet. The previously observed CS₂ trimer has a barrel-shaped structure with three equivalent monomers and D₃ symmetry. The new isomer consists of a staggered parallel “dimer pair” of equivalent CS₂ monomers with a third CS₂ monomer sitting “on top”, similar to the known non-cyclic CO₂ trimer. This structure has C₂ rotational symmetry corresponding to the b inertial axis of the trimer, as proven by observed nuclear spin statistics. Ab initio calculations correctly give the two observed isomer structures and indicate that they lie very close in binding energy.

Neutral and ionic N₂ species exhibit a rich spectrum as a result of the large density of couplings between states with different multiplicities. In this sense, spectra of the molecular ion N${}_2^{+}$ are investigated combining Fourier transform spectroscopy and ab initio methods. We have reanalyzed the First Negative band System (B${}^2{\Sigma }_u^{+}$ $\to$ X${}^2{\Sigma }_g^{+}$) including five bands not reported previously by Fourier spectroscopy. The spectra were recorded using a resolution of 0.6 cm⁻¹ and accuracy of 0.005 cm⁻¹. These results are then compared with new MRCI+Q/AV6Z calculations. For the first time, transition probabilities are computed for the previously observed 2${}^2{\Pi }_g$-A${}^2{\Pi }_u$ band system. The 2${}^2{\Pi }_g$ state ($T_e$ = 67,029 cm⁻¹) has a dissociation energy of 24,787 cm⁻¹ at $R_e$ = 2.7332 a₀. The predicted lifetimes for the 2${}^2{\Pi }_g$-A${}^2{\Pi }_u$ emissions are of the order of 170 ns. The calculated transition probabilities A($v^{\prime }$=0, $v^{\prime \prime }$=0) for the B${}^2{\Sigma }_u^{+}$-X${}^2{\Sigma }_g^{+}$ and 2