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Results of quantum calculations on rotationally and vibrationally inelastic scattering of rotationally excited 1Au(S1) trans‐glyoxal (in collisions with H2, at a collision energy of 80 meV) are reported. These results are used to assess the influence of sequential collisions on a recent experiment on glyoxal +H2. For ‖ΔK‖>3, the cross sections for rotationally inelastic scattering σ(00,K=k→00,K’=K+ΔK) depend exponentially on (ΔK)2 (and not on the energy difference between the initial and final states), which shows that the rotationally inelastic scattering is dominated by angular momentum transfer rather than by energy transfer. Taking into account sequential collisions leads to a substantial improvement in the agreement between the calculated and experimental values of the rotationally resolved cross sections for excitation of the lowest frequency ν7 torsional mode.

In this paper we present results of simulations of an electron in dense helium with ground state dominance, at 309 K and reduced densities ρ*=0.25, 0.50, and 0.90. Some results at ρ*=1.10 and T=309 K and at ρ*=0.25, T=77 K are also presented and discussed. From the mean square displacement of the electron, the diffusion coefficient and mobility was computed. Properties of six eigenstates with the lowest energy eigenvalues of instantaneous configurations are presented and discussed. The energy eigenvalues of the instantaneous potentials are compared with an eigenvalue spectrum computed with a spectral method. They are also compared with the energy eigenvalues obtained from the mean radial potential felt by the electron.

Using the AVCC-1OS (azimuthal and vibrational close-coupled, infinite-order sudden) method, we have calculated efficiencies for vibrational relaxation of glyoxal in collisions with He and Ar at room temperature. For glyoxal- d 2 (deuterated glyoxal) + He the calculated efficiency P ( 0°, k = 0→7 1 ) is in reasonable agreement with experiment, but for glyoxal- d 2 + Ar the calculated v of P(0°, k =0→7 1 ) is much lower than the experimental value. While part of the discrepancy may be due to the sudden approximation (to the sl nevertheless suggest that, especially for heavier collision partners, the experimental values of P (0°→7 1 ) should be much too high because the question of how rotational relaxation should affect the measurement of vibrationally relaxed and unrelaxed emission was not considered in the experiment. For glyoxal- d 2 + He, the calculated efficiencies P (8 1 →6 1 ) and P (8 1 →8 1 7 1 ) agreement with experiment. Because the frequency difference between the ν 6 and the ν 8 modes is much smaller in glyoxal- h 2 (“normal” or protonated glyoxal), for glyoxal- h 2 + He the calculated efficiency P (8 1 →6 1 ) is much higher than for glyoxal- d 2 + He.

Results of quantum calculations on rotationally and vibrationally inelastic scattering of rotationally excited 1Au(S1) trans‐glyoxal (in collisions with H2, at a collision energy of 80 meV) are reported. These results are used to assess the influence of sequential collisions on a recent experiment on glyoxal +H2. For ‖ΔK‖>3, the cross sections for rotationally inelastic scattering σ(00,K=k→00,K’=K+ΔK) depend exponentially on (ΔK)2 (and not on the energy difference between the initial and final states), which shows that the rotationally inelastic scattering is dominated by angular momentum transfer rather than by energy transfer. Taking into account sequential collisions leads to a substantial improvement in the agreement between the calculated and experimental values of the rotationally resolved cross sections for excitation of the lowest frequency ν7 torsional mode.

Results of quantum calculations on rotationally and vibrationally inelastic scattering from four vibrational levels of 1 A u (S 1 ) trans-glyoxal (in collisions with helium, at a collision energy of 96 meV) are reported. The results can serve as predictions to be borne out by experiments that have already been carried out, but have not been analyzed yet. The calculations predict that rotationally inelastic scattering should be similar for scattering from the 0 0 , 5 1 and 8 1 levels, but different for scattering from the 7 2 level. A comparison of the glyoxal+He results with results for scattering of vibrationless deuterated glyoxal also presented here shows that, at a collision energy of 96 meV, rotational excitation of glyoxal by helium is governed by angular momentum transfer rather than by energy transfer. Vibrationally inelastic scattering is dominated by the lowest frequency ν 7 torsional mode, but the calculations predict that transitions involving other vibrational modes should also be observable.

Results of quantum calculations on rotationally and vibrationally inelastic scattering of 1Au(S1) trans‐glyoxal by H2,He, and Ar(E=80 meV) are presented. For scattering of 00 glyoxal and 72 glyoxal by H2, a quantitative comparison with a recent crossed beam experiment is made. The calculated cross sections for rotationally inelastic scattering are in good agreement with the experimental values, and the trend that σ(72, k=0→72, k’) falls off faster with k’ than σ(00, k=0→00, k’) is reproduced. Our calculations do not reproduce the experimental finding that, for the initial 72 level, the cross sections for the Δv7=−1 and Δv7=+1 transitions are nearly identical. The calculations on 72 glyoxal + He and Ar show important differences with 72 glyoxal + H2 in the competition of rotational excitation with vibrational excitation. Model calculations also presented here yield some interesting trends in the k’ dependence of the cross sections σ(00, k=0→x1, k’) on the vibrational mode x excited.

Using the Monte Carlo classical trajectory (CT) method and the azimuthal close‐coupled, infinite‐order sudden (ACC‐IOS) method, we have calculated cross sections for rotational excitation of S1 trans‐glyoxal by H2 at E=80 meV. The cross sections σ(k=0, j→k’) calculated with the CT method are nearly independent of j. The classical values of σ(k=0, j=5→k’) are in good agreement with the quantum values of σ(k=0→k’) for 2≤k’≤12, although the quantum calculations show a slight preference for odd Δk transitions which is not found in the CT calculations. Both the CT results and the ACC‐IOS results are in good agreement with results obtained in a recent crossed beam experiment. Rotational excitation to high k’ (k’=11,12) occurs by collisions of H2 with one of the H atoms of glyoxal, and the initial value of the orbital angular momentum approximately equals the final value of k in such collisions. Since backward scattering is dominant in collisions leading to high k’, angular momentum constraints alone cannot expl...

Results of quantum calculations on rotationally and vibrationally inelastic scattering of 1Au(S1) trans‐glyoxal by H2,He, and Ar(E=80 meV) are presented. For scattering of 00 glyoxal and 72 glyoxal by H2, a quantitative comparison with a recent crossed beam experiment is made. The calculated cross sections for rotationally inelastic scattering are in good agreement with the experimental values, and the trend that σ(72, k=0→72, k’) falls off faster with k’ than σ(00, k=0→00, k’) is reproduced. Our calculations do not reproduce the experimental finding that, for the initial 72 level, the cross sections for the Δv7=−1 and Δv7=+1 transitions are nearly identical. The calculations on 72 glyoxal + He and Ar show important differences with 72 glyoxal + H2 in the competition of rotational excitation with vibrational excitation. Model calculations also presented here yield some interesting trends in the k’ dependence of the cross sections σ(00, k=0→x1, k’) on the vibrational mode x excited.

Using the Monte Carlo classical trajectory method, we have calculated cross sections for complex formation and complex lifetimes for glyoxal–helium collisions at low relative translational energies (

s-Tetrazine argon complexes T−Arn (n = 1, 2) are formed in a supersonic expansion of argon seeded with s-tetrazine. The expansion was conducted through a nozzle of 50 or 100 μm with an argon stagnation pressure between 1 and 1.5 bar. From spectrally resolved measurements it is clear that vibrational redistribution processes as well as vibrational predissociation processes take place after SVL excitation within the complex.From rise and decay time experiments it can be concluded, that after excitation of the 6a1 complex level, the above mentioned processes are consecutive and not parallel. It appears that the out of plane mode 16a couples with the Van der Waals stretching mode. The predissociation rate of the 16a2 complex is observed to be 2.3 × 109 s−1.

The phosphorescence of phenanthrene, pyrene, and naphthalene in fluid solutions has been studied. The radiative lifetimes are calculated from the quantum yields and actual lifetimes and vary only slightly or not at all with temperature within the experimental error. For phenanthrene, pyrene, naphthalene, and anthracene the radiative lifetimes at 77°K in ethanol are 25, 30, 75, and 180 sec, respectively. The temperature dependence and the absolute value of the triplet–triplet annihilation efficiency vary from molecule to molecule. The results are discussed in terms of a re‐encounter association of the annihilation partners to form an excimer.

The “molecules in molecules” method has been used to calculate the energies of the lowest four excited states of the decacyclene molecule which has been regarded as composed of three acenaphtylene biradicals. Comparison with experimental data and previous theoretical results shows that the results obtained with the present method are satisfactory.

Absorption and emission spectra of decacyclene are presented. The experimental data are compared with the results of configuration interaction calculations of the Pariser‐Parr type including doubly excited configurations. The agreement between the experimental and the calculated term schemes is satisfactory for the lower excited states. It can be shown that the S0‐S1 transition is symmetry forbidden.

The fluorescence and fluorescence excitation spectra of the dimer of 9, 10‐diazaphenanthrene are given with the relative degrees of polarization of the bands. The stabilization enthalpy of the dimer is 3.6 kcal mole−1, and the association constant K = 9.1 × 10−2exp(1800 / T) for 100°K ≤ T ≤ 130°K.

The absorption intensities of eight different induced transitions have been measured in the spectral region from 7500 to 28 000 cm−1 at constant densities (about 130 amagat units). The measurements were carried out at temperatures from 350°K down to 165°K. The results are discussed on the basis of a simple model for the gas in which it is assumed that the absorption is due to bound dimers as well as collision pairs. Absorption cross sections are evaluated for these two species.