K.W. McLaughlin

Production of excited atomic hydrogen and deuterium from H2and D2photodissociation

We have measured the production of both Lya and Ha fluorescence from atomic H and D for the photodissociation of H 2 and D 2 by linearly polarized photons with energies between 24 and 60 eV. In this energy range, excited photofragments result primarily from he production of doubly excited molecular species which promptly autoionize or dissociate into two neutrals. Our data are compared with ab initio calculations of the dissociation process, in which both doubly excited state production and prompt ionization (non-resonant) channels are considered. Agreement between our experimental data and that of earlier work, and with our theoretical calculations, is qualitative at best.

Production of excited atomic hydrogen and deuterium from H2 and D2 photodissociation

We have measured the production of Lyman α and Balmer α fluorescence from atomic H and D for the photodissociation of H2, HD and D2 by linearly-polarized photons with energies between 22 and 64 eV. We discuss systematic uncertainties associated with our data, and compare our results with previous experimental results and ab initio calculations of the dissociation process. We comment on the discrepancies. (Some figures in this article are in colour only in the electronic version)

Production of excited atomic hydrogen and deuterium from H2, HD and D2 photodissociation

We have measured the production of both Lyα and Hα fluorescence from atomic H and D for the photodissociation of H2 and D2 by linearly polarized photons with energies between 24 and 60 eV. In this energy range, excited photofragments result primarily from the production of doubly excited molecular species which promptly autoionize or dissociate into two neutrals. Our data are compared with ab initio calculations of the dissociation process, in which both doubly excited state production and prompt ionization (nonresonant) channels are considered. Agreement between our experimental data and that of earlier work, and with our theoretical calculations, is qualitative at best. (Some figures in this article are in colour only in the electronic version)

Use of partial-wave decomposition to identify resonant interference effects in the photoionization?excitation of argon

We have studied simultaneous photoionization and excitation of Ar in the range of incident photon energies between 36.00 and 36.36 eV, where the resonant production of doubly excited neutral Ar states imbedded in the ionization continuum is dominant. By measuring the relative Stokes parameters of the fluorescence from residual Ar +∗ (3p 4 [ 3 P] 4p) ions ( 2 P1/2, 465.8 nm transition; 2 P3/2, 476.5 nm; 2 D3/2, 472.7 nm; 2 D5/2, 488.0 nm; 4 P5/2, 480.6 nm; 4 D5/2, 514.5 nm) we demonstrate a technique for determining individual partial-wave cross sections in photoionizing collisions. This procedure is shown to be important in sorting out competing dynamical ionization mechanisms, particularly with regard to resonant production of intermediate doubly excited autoionizing states. Comparison with theoretical photoionization cross sections demonstrates that spin–orbit coupling between different states of Ar II needs to be accounted for in the calculations. (Some figures in this article are in colour only in the electronic version)

Angular Momentum Partitioning in the Dissociation of Diatomic Molecules

We discuss recent experiments that study the transfer of angular momentum from a projectile to the residual target in collisions between the simple diatomic molecules H2 and N2 and spin‐polarized electrons or circularly‐polarized photons. We observe the fluorescence of both the atomic fragments and excited molecular states, and measure the circular polarization fraction of this light, P3. The incident electron energies range from 10 to 100 eV; the incident photon energies from 33 to 38 eV.