Articles you may be interested inLaser induced fluorescence measurements of microwave stimulated OH molecules from H2O photodissociation Lymanα, Lymanα coincidence detection in the photodissociation of doubly excited molecular hydrogen into two H(2p) atoms J. Chem. Phys. 88, 3016 (1988); 10.1063/1.453943 H Lymanα emission from photodissociation of H2OThe polarization of the Lyman-␣ fluorescence following photodissociation of H 2 and D 2 into fragments in the 1s and 2l states has been determined as a function of the excess energy of the fragments. The predicted oscillations of the polarization as a function of excess energy were clearly observed. In addition, the theoretical polarization was recalculated including the stronger B -BЈ coupling scheme as well as collisional effects on the polarization. The collisional effects include the quenching processes for H(2s) and H(2p) and disaligning collisions. The calculations reproduced the experimental data quite well giving a cross section for the disaligning collisions of ͑1.0Ϯ0.2͒•10 Ϫ14 cm 2 for H 2 and D 2 at a gas temperature of 137 K in the relative velocity range of 2 to 7 km s Ϫ1 . This can be considered as a proof of the theoretical predictions on the interference effects between the continua excited coherently.

The de-excitation cross sections of H(3l) atoms colliding with molecular hydrogen (T = 300 K) were determined in the velocity range of 2-7 km s −1 . At a mean velocity of 5 km s −1 the de-excitation cross sections are σ 3s = 170 ± 7 Å2 , σ 3d = 129 ± 7 Å2 andThe velocity dependence of the de-excitation cross sections observed in the experiment agrees with the H 2 quadrupole-H dipole interaction and with the quantum character of the molecular rotation.

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The polarization anisotropy of Lyman-α fluorescence in the photodissociation of the doubly excited states of H2 has been measured in the 27–38 eV energy range. It has been calculated taking into account the dissociation probabilities of the various molecular states involved in the process and the depolarization due to collisional effects. The agreement between experiment and theory is very good; it shows the importance of interferences and gives confidence in the analysis of the process. The fluorescence polarization anisotropy has been calculated classically in the case of a dissociation leading to H(2pπ) + H(2pσ) excited fragments.