Z. X. He

Production of N+∗ from N2 + hv: Effective EUV emission yields from laboratory and dayglow data

Abstract Photodissociative ionization of N2 into the unbound N + 2 H 2 Σ g + state is identified as the parentage of a number of N+ and N excited states that contribute to the u.v. dayglow. Yields have been obtained for the production of extreme ultraviolet emission lines of N+ (and N) from a laboratory experiment using a broad-band synchrotron radiation source with fluorescence spectroscopy. The yields are termed “effective”, in that they are constant percentages of the H state cross section. These are compared with effective yields needed to reproduce NII 1085 and 916 A lines from four dayglow observations using a model of solar energy deposition and photoelectron production and loss in the Earths thermosphere. The 1085 A effective yield measured in the laboratory (18%) agrees with that from the dayglow data (average of 17%) to well within experimental uncertainties. Thus, we conclude that photodissociative ionization of N2 is the primary source of the Nil 1085 A dayglow. However, there is an order of magnitude discrepancy among the various dayglow observations of the 1085/916 intensity ratio, only one of which is consistent with the laboratory observation of 4.4. Neither contamination by other dayglow features nor atmospheric extinction can account for the disparities. Laboratory measurements of N2 and O2 absorption cross sections at these wavelengths are also reported.

DISSOCIATIVE PHOTOIONIZATION CROSS SECTIONS OF N2AND O2FROM 100 TO 800 eV

We report measured partial cross sections for the fragments from dissociative photoionization of N2 and O2 over the photon energy range of 100 to 800 eV. The partial cross sections were found to follow a power law of the form (hn), where hn is the incident photon energy. The exponent, a, is shown to be near 2.7 for N 2 and for all N2 partial cross sections above the nitrogen K-edge. An exponent of 3.0 was found for O 2 and for all O2 partial cross sections above the oxygen Kedge. q 1998 Academic Press

Zero kinetic energy proton and deuteron production from photoionization of H2 and D2

A zero ion kinetic energy spectrometer has been developed to study the production of near zero energy protons and deuterons from dissociative photoionization of H2 and D2. Both H+ and D+ spectra show four peaks on top of a continuum. The continuum was found to be in excellent agreement with the single center Coulomb calculation for the direct dissociation through the X 2Σ+g state of H+2. The observed structures were shown to originate from autoionization of the doubly excited Q1 1Σ+g(1), Q1 1Σ+u(1), Q1 1Σ+u(2), and Q2 1Σ+u(1) states, of which the Q1 1Σ+g(1) state is dipole forbidden.

Multiple photoionization of free atoms

A brief review is given of the present status of the He2+/He+ ratio, the effect of Compton scattering on this ratio, and the effect of post-collision-interaction on the Auger decay of an Ar L-shell vacancy.

Dissociative photoionization cross sections of Na and O2 from100 to 800 eV

We report measured partial cross sections for the fragments from dissociative photoionization of N2 and O2 over the photon energy range of 100 to 800 eV. The partial cross sections were found to follow a power law of the form (hn), where hn is the incident photon energy. The exponent, a, is shown to be near 2.7 for N 2 and for all N2 partial cross sections above the nitrogen K-edge. An exponent of 3.0 was found for O 2 and for all O2 partial cross sections above the oxygen Kedge. q 1998 Academic Press

Dissociative photoionization cross sections of N{sub 2} and O{sub 2} from 100 to 800 eV

We report measured partial cross sections for the fragments from dissociative photoionization of N2 and O2 over the photon energy range of 100 to 800 eV. The partial cross sections were found to follow a power law of the form (hn), where hn is the incident photon energy. The exponent, a, is shown to be near 2.7 for N 2 and for all N2 partial cross sections above the nitrogen K-edge. An exponent of 3.0 was found for O 2 and for all O2 partial cross sections above the oxygen Kedge. q 1998 Academic Press