A. Karawajczyk

Direct Determination of the Ionization-potential of Co By Resonantly Enhanced Multiphoton Ionization Mass-spectroscopy

Direct determination of the ionization potential of CO by resonantly enhanced multiphoton ionization mass spectroscopy

Photoionization and photodissociation of nitric oxide in the range 9–35 eV

Photoionization and photodissociation of NO has been studied using 9–35 eV synchrotron light and detection of fluorescence as well as of mass selected NO+, N+, O+, and O− ions. Rydberg series converging to all known states in NO+ below 24 eV have been analyzed and classified and several of them are found to be predissociated by various NO+ states as well as by NO ion pair states. The complex structure in the 950–1200 A excitation region is suggested to originate from interaction between a ‘‘new’’ NO valence state at T0=77 470 cm−1 and high vibrational levels of Rydberg series converging to the NO+ ground state.

State selective photon induced formation of triply charged fragments from the core excited OCS molecule

State selective photon induced formation of triply charged fragments from the core excited OCS molecule

Dissociative photoexcitation of CH4 and CD4

Abstract Fluorescence emission spectra and ion-yield spectra of CH 4 and CD 4 have been measured using monochromatic synchrotron radiation. We have studied the X and A ionic states in the 12–30 eV region (400–1000 A). The visible fluorescence measurements focus upon the Rydberg series converging to vibrational levels of the A state at 22.39 eV; this structure is also reflected in some of the charged fragments including the parent ion indicating that these Rydberg states may autoionize. The character of the Rydberg states is discussed, and a comparison with negative-ion fragment spectra is made.

Lifetime measurements of excited molecular states using a Ti:sapphire laser. Radiative lifetimes of the B 2Σ+ and C 2Π states of BaBr

Abstract The barium bromide monohalide has been studied by using laser resonance methods in the near-infrared and green-blue wavelength regions. The low-lying B 2 Σ + state has been investigated in a time-resolved experiment using a Ti:sapphire laser operating around 900 nm. No influence on the radiative lifetime due to the B 2 Σ interaction with the A′ 2 Δ-A 2 Π complex was observed. The radiative lifetime of the C 2 ]gP state was examined using the 514.5 nm Ar + laser line. The derived lifetime of this state was in agreement with earlier measurements. The following lifetimes were obtained for the BaBr molecule: B 2 Σ 2 123.2 ± 0.5 ns and C 2 Π 3 2 16.9 ± 0.1 ns.

Synchrotron radiation study of photoionization and photodissociation processes of CO2 in the 13-21 eV region

A study of synchrotron radiation induced photoionization and photodissociation of CO2 has been performed using the Swedish national synchrotron facility Max in Lund. Monochromatic synchrotron radiation, in the 10-30 eV region, has been used to obtain mass spectra of the CO2+, CO+, O+, and C+ ions. The observed structure is interpreted in terms of autoionization and photodissociation processes via excited Rydberg states in CO2 converging to the ionic X2 Pi g, A2 Pi u, B2 Sigma u+, and C2 Sigma u+ states. In the CO2+ ion yield measurements, new progressions are assigned as members of a Rydberg series converging to the A-state for which only the n*=2.5 member has been observed before. A transition to the bent valence state has been recorded and discussed. Fluorescence spectra obtained in the visible and VUV regions support ion yield results. Furthermore, structures originating from resonant autoionization have been found.

Studies of fluorescence from photoionization and photodissociation of N2 induced by 16-40 eV synchrotron radiation

Molecular nitrogen has been exposed to synchrotron radiation in the range 16-40 eV and the resulting fluorescence has been studied in various regions from 1100-8500 AA. Line structures are observed which are interpreted in terms of autoionization or dissociation of well known Rydberg states in N2 converging to the B, C and D states in N2+. In addition a new member of the Rydberg series converging to the D state is found.

Soft x-ray photoionization and fragmentation of SO2 studied by threshold photoelectron-photoion-photoion coincidence (TPEPIPICO) spectroscopy

The photoionization of SO2 has been studied in the photon energy range 160-560 eV using the SRS at Daresbury Laboratory, UK. Threshold photoelectron and total ion-yield spectra are presented in the region of the S 2p and O 1s edges. Ion branching ratios are obtained from threshold photoelectron-photoion coincidence (TPEPICO) data and the detailed dynamics of the fragmentation process determined using the threshold photoelectron-photoion-photoion coincidence (TPEPIPICO) technique. The data are compared with other results at the S 2p edges, and with previous studies of SO2 in the vacuum ultraviolet spectral region.

Energy distributions of ions produced in photodissociation of in the 17 - 34 eV range

Energy distributions of ions from photodissociation of in the 17 - 34 eV energy range have been measured using photoelectron - photoion TOF spectroscopy. A high accuracy in the determination of the kinetic energies of the released fragments allows for a qualitative comparison of the different dissociation processes. In the lower energy region (17 - 20.5 eV) the production of fragments occurs mainly via resonant processes like post-dissociative autoionization (PDI), autoionization to dissociative states of the ion or dissociation from the ion pair state. In the higher energy region the fragmentation most frequently occurs due to direct photoionization to dissociative states of the ion, although the presence of PDI has also been observed. No fragments are observed with kinetic energies higher than 2 eV.

Visible and VUV fluorescence from synchrotron radiation induced photoionization and photodissociation of molecular oxygen

Photon induced fluorescence from O2 has been studied in various emission regions 1150-6500 A in the excitation range 14-28eV using the Swedish synchrotron facility MAX in Lund. A rich line structure is observed which is interpreted in terms of autoionization and dissociation of Rydberg levels converging to the a, b, c, and B states in O2+. New features have been observed, for instance, concerning the (c 4Σu−) 3sσg Fano resonance which has been viewed in detail in different detection channels including O2+ and O+ ions.