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Photodissociation processes of the doubly excited states of H2 into H(2p)+H(2p) have been studied using a coincidence detection of two Lyman-α photons. Coincidence spectra have been measured in the energy region of 29.0–36.0 eV. The intensity of the observed coincidence peak corresponding to two Lyman-α photons increases with increasing energy from its threshold which is about 29 eV. The main precursor of the two H(2p) atoms is assigned to the doubly excited Q2 1Πu state.

The dissociative recombination of hydrocarbon ions. II. Alkene and alkyne derived speciesThe isotope exchange reaction of fast hydrogen atoms with deuterated alkynes and alkenes J. Chem. Phys. 92, 206 (1990); 10.1063/1.458464 Ionization in liquid hydrocarbons: γ radiolysis yields and electron range distribution functions Free ion yields have been measured as functions of temperature T and electric field strength E in hydrocarbon liquids. A range distribution of the secondary electrons in hydrocarbons, suitable for use in the one-ion-pair-per-spur model, iswhere F(y)dy is the fraction of thermalized electron-ion pairs that have initial separation distances between y and y + dy, and b GP is the dispersion parameter. This equation is suitable for all of the liquids that have been studied thus far, at all values of T and E that have been used. The value of bGpd for a given liquid is independent of T, where d is the liquid density. The density-normalized ranges in a family of hydrocarbons with the same number of carbon atoms and analogous carbon skeletons decrease in the order alkane> alkene-I> alkyne-l. Two terminal double bonds are more effective than one terminal triple bond in reducing the electron range. Conjugation of the double bonds appears to have no special influence on electron de-energization. The range in a trans-alkene-2 is essentially the same as that in the corresponding alkene-I, but otherwise, internal double bonds are less effective than terminal double bonds in de-energizing the electrons. Ranges in cis-alkenes are greater than those in the corresponding trans-alkenes. Increasing the amount of chain branching in a family of alkanes or alkenes increases the electron range. An internal triple bond increases the range over that in an alkane.

Electron drift mobilities μe and electron–ion recombination rate constants kr in gaseous, liquid, and solid argon have been measured by the analysis of transient current induced with the irradiation of an x-ray pulse as functions of temperature and external electric field strength except solid. The effect of external dc electric field on kr up to ∼3×10−3 Td (1 Td=10−17 V cm2/molecule) was examined in gaseous and liquid phases. The observed kr values in both liquid and gas phases were found to be much smaller than those calculated by the reduced Debye equation. The deviation, which is bigger in gas than in liquid, has been compared with recent theoretical studies1–5 which were presented to explain our previous data on the kr values for methane.6 It has been concluded that the recombination also in liquid and gaseous argon is not a usual diffusion-controlled reaction. In the solid phase the observed kr values were almost in agreement with those calculated by the reduced Debye equation. The electron–ion recombination rate constants in both liquid and gas phases increased almost linearly with an external dc electric field up to a critical electric field strength below which electron mobility was nearly constant, and decreased with further increase in the electric field where electron mobility also decreased.

Absolute measurements of the photoionization and photodissociation cross sections of C H h b d · .2 2 ave een rna e usmg contmuum monochromatized synchrotron radiation in the 53-93 nm region. The absolute photoabsorption cross section and photoionization quantum yield of C 2 H 2 have also been measured. The excitation spectra ofC, and H(Lyman-a) fluorescence have also been obtained. The obtained results have been compared with theoretical calculations. An unresolved problem of the spectral. interpretation concentrated on the (J * and 1T* shape resonances has been clarified by the ~tr~l~htforward demonstration of the photoionization quantum yield. The ionizing and nomomzmg decay processes of the superexcited C Z H 2 molecules have been discussed in view of the strong competition of autoionization and neutral dissociation. An overlapping nature of Rydberg states with the shape resonance is found to be important. 4142