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Photoemission cross sections (σem) for the A–X, B–X, and C–X bands of CH resulting from the He(23S)+CH3X (X=H, Cl, Br, I) reaction have been studied in the relative collision energy (ER) of 120–210 meV. Formation cross sections (σ) for CH(A, B, C) were evaluated from the σem’s taking account of predissociation. A good correlation was found between the sum of the σ’s for CH and the dipole-induced dipole interaction of He(2 3S) with targets. The σem’s from methane increase with ER, while those from methyl halides decrease with increasing ER. The positive energy dependence for methane implies that effective potentials leading to CH are repulsive, whereas attractive potentials play a dominant role in the reaction of He(2 3S) with methyl halides. Model potentials between CH3Cl and He*(Li) calculated using ab initio molecular orbital methods indicate that He(2 3S) approaches CH3Cl not from CH3 side but from Cl side.

Emissions in the 200–750 nm region produced by the collision of He*(2 3S) with H2S were studied under single-collision conditions. The hydrogen Balmer lines and the SH+(A 3Π–X 3Σ-) and H2S+(A˜ 2A1–X˜ 2B1) bands were assigned. The total emission cross section (σem) was evaluated to be (1.7±0.3)×10-20 m2 at a collision energy of 150 meV. The σems of the SH+(A–X) and H2S+(A˜ –X˜ ) bands decreased with increase in the collision energy in the 115–200 meV range, indicating that attractive forces are effective for the incident channels with regard to the formation of these species. The rotational distribution of SH+(A 3Π,ν'=0) is represented by a Boltzmann temperature of 870±80 K. The H2S+(A˜ 2A1–X˜ 2B1) emission, which was assigned for the first time in the Penning ionization of H2S, primarily consists of the bending progressions. The internal populations of H2S+(A˜ ) were analyzed using the vibrational energies and Einstein's A coefficients calculated in this study. The details of the calculation and derived spectroscopic constants are reported in the accompanying paper, Paper I. The populations obtained for the bending vibration (ν' 2) of H2S+(A˜ ) show an inverted distribution with a peak at ν' 2=3. This distribution is shifted lower compared that with a peak at ν' 2=4 – 5 observed by He*(2 3S) Penning ionization electron spectroscopy and that with a peak at ν' 2=6 – 7 predicted by the theoretical Franck–Condon factors for the H2S(X˜ )–H2S1(A˜ ) ionization. The origin of the difference is discussed concerning the formation mechanism of H2S1(A˜ 2A1).

Transition probabilities were evaluated for the X˜ 1A1-A˜ 1B1 and A˜ 1B1-B˜ 1A1 systems of SiH2 and SiD2 to analyze the X˜→A˜→B˜ photoexcitation. The Franck–Condon factors (FCFs) and Einstein's B coefficients were computed by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of the SiH2(X˜ 1A1 ,A˜ 1B1 ,B˜ 1A1) electronic states and the electronic transition moments for the X˜ -A˜, X˜ -B˜, and A˜ -B˜ system. The global PESs were determined by the multireference configuration interaction calculations with the Davidson correction and the interpolant moving least-squares method combined with the Shepard interpolation. The obtained FCFs for the X˜ -A˜ and A˜ -B˜ systems exhibit that the bending mode is strongly enhanced in the excitation since the equilibrium bond angle greatly varies with the three states; the barrier to linearity is evaluated to be 21 900 cm-1 for the X˜ state, 6400 cm-1 for the A˜ state, and 230–240 cm-1 for the B˜ state. The theoretical lifetimes for the pure bending levels of the A˜ and B˜ states were calculated from the fluorescence decay rates for the A˜ -X˜, B˜ -A˜, and B˜ -X˜ emissions.

Photoabsorption cross sections of thiirane and thietane vapors have been studied in the 110–240 nm region using synchrotron radiation. A number of peaks from thiirane and thietane are arranged into four and five Rydberg series, respectively, converging to the first ionization potential. Many Rydberg peaks from both molecules are observed to possess vibronic structures. The vibrational progressions from thiirane are assigned to the CH2 wagging (ν4) and CS symmetry stretching (ν5) modes. For thietane, the CH2 wagging (ν5) and CS symmetry stretching (ν7) modes of the excited states are found to be active. Molecular geometries and vibrational frequencies for the excited states are discussed on the basis of ab initio calculations.