Photodissociation of hydrogen halides

PHOTODISSOCIATION OF HYDROGEN HALIDES IN A CRYOGENIC RARE GAS ENVIRONMENT A COMPLEX APPROACH TO SIMULATIONS OF CLUSTER EXPERIMENTS... 

Buck, U. 2002, Photodissociation of hydrogen halide molecules in different clnster... 

Photodissociation of hydrogen halides in a cryogenic rare gas environment a complex approach to simulations of cluster experiments 467... 

In early days, HRTOF technique was used to study gas-phase photodissociation whose products contain hydrogen atoms (or deuterium atoms), for example, a variety of hydrogen halides, HCN, H2O, H2S, NHj, PHj, C2H2, CH3SH, CH3NH2, HCOOH, HFCO, HN3 [8, 10, 37]. These processes constitute a major chemical... 

VI-2.2 Energy Partitioning in Photodissociation of H,S. 205 VI-.7 Hydrogen Cyanide (IICN), 206 VI-3.1 Photochemistry, 206 VI-4 Cyanogen Halides, 206... 

Let us consider how independent /i(i ) 2 effects contribute to the v E) for the hydrogen halides, HX (X = I, Br, and Cl). The curves shown on Fig. 7.6 correspond to relativistic adiabatic potential energy curves (respectively 0 dotted, 0+ dashed, 1 and 2 solid) for HI obtained after diagonalization of the electronic plus spin-orbit Hamiltonians (see Section 3.1.2.2). The strong R-dependence of the electronic transition moment reflects the independence of the relative contributions of the case(a) A-S-Q basis states to each relativistic adiabatic II state. The independent experimental photodissociation cross sections are plotted as solid curves in Fig. 7.7 for HI and HBr. Note that, in addition to the independent variations in the A — S characters of each fl-state caused by All = 0 spin-orbit interactions, all transitions from the X1E+ state to states that dissociate to the X(2P) + H(2S) limit are forbidden in the separated atom limit because they are at best (2Pi/2 <— 2P3/2) parity forbidden electric dipole transitions on the X atom. In the case of the continuum region of an attractive potential, the energy dependence of the dissociation cross section exhibits continuity in the Franck-Condon factor density (see Fig. 7.18 Allison and Dalgarno, 1971 Smith, 1971 Allison and Stwalley, 1973). 

To illustrate the significance of measurements of internal state branching ratios, we will turn once again to the example of the photodissociation of the hydrogen halides, HX. The fine structure ratio is the branching ratio of X /X populations 2Pi/2/2P3/2- In the non-relativistic adiabatic representation, this branching ratio would be predicted to be zero because the only case (a) basis state which has a non-zero transition moment from the X1E+ state is the 1IIi state which correlates adiabatically with the X(2P3/2) +H(2S) separated atom limit. However, in the more realistic relativistic adiabatic representation, Afl = 0 3E/, 1n3 3ni, and 3ni 3Ei" spin-orbit matrix elements... 

Cyanogen Halides, Hydrogen Cyanide, and Cyanogen.—Studies of energy disposal in the near u.v. photodissociation of ICN have had a chequered career. In an early flash photolysis experiment it was concluded that CN was formed in its ground electronic state with little or no vibrational excitation. Subsequent theoretical treatments all agreed that this was a respectable conclusion but new... 

Studies of vibrational (and rotational) energy disposal in the vacuum u.v. photodissociation of cyanogen, hydrogen cyanide, and the cyanogen halides, were reported by Mele and Okabe and the estimated vibrational distributions in the dissociations... 

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