Photoelectron angular distributions from rotationally resolved autoionizing states of N2

Abstract

The single-photon, photoelectron-photoion coincidence spectrum of N 2 has been recorded at high (∼1.5 cm 1 ) resolution in the region between the N 2 + X 2 Σ g + , v + = 0 and 1 ionization thresholds by using a double-imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N 2 + X 2 Σ g + ground state, and electronically autoionizing states converging to the N 2 + A 2 Π and B 2 Σ u + states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. A simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, β, and the results are in reasonably good agreement with experiment. Published by AIP Publishing.

Dissociation of State-Selected Ions Studied by Fixed-Photon-Energy Double-Imaging Photoelectron Photoion Coincidence: Cases of O2+ and CH3F+

“…In addition, in agreement with our previous results [31,43], the CH 2 + (m/z = 14) and CHF + (m/z = 32) fragment ions with weak signals are identified in the mass spectrum as well. The mass peak at m/z = 35 represents ~1% of the CH 3 F + peak and is identified as the 13 CH 3 F + isotopic parent ion.…”

“…(ii) A broadband continuum light source, such as an Ar or He Hopfield continuum discharge lamp and synchrotron radiation, is equipped with a VUV monochromator. This equipment is then used to scan through various ionic states, analyzing either all the photoelectrons in coincidence with a given ion-to measure mass-tagged photoionization efficiency (PIE) curves [12] or angle-resolved constant-ionic-state (CIS) spectra [13,14]-or only near-zero kinetic energy electrons, commonly referred to as threshold photoelectrons, in the so-called threshold PEPICO (TPEPICO) scheme [15,16]. TPEPICO has the advantages of high collection efficiency and high-energy resolution for threshold photoelectrons, particularly when the strategy of electron velocity-map imaging (VMI) is used [17,18].…”

Photoionization studies of reactive intermediates using synchrotron radiation

“…115). This method (116) has the added advantage that CIS plots can be obtained and β-parameters can be recorded as a function of photon energy (117,118). These subtraction methods, using the VMI technique, have the great advantage of operating in a fully continuous mode, which are well adapted to a synchrotron source operated in multibunch mode and for which application of TPEPICO is straightforward.…”

Double-resonance studies of electronically autoionizing states of molecular nitrogen

“…For the case of N 2 , photoionization is from the a" 1 Σ g + , v = 0, J level into the N 2 + 2 Σ g + , v + , N + + εℓ continua. 2 If we assume that autoionization of the A + (v)4dπ 1 Σ u + state goes into the ℓ = 1 (εp) continuum, the corresponding formula for β are identical. 2 Specifically, the rotationally resolved β values are given by: 1,2…”

“…2 If we assume that autoionization of the A + (v)4dπ 1 Σ u + state goes into the ℓ = 1 (εp) continuum, the corresponding formula for β are identical. 2 Specifically, the rotationally resolved β values are given by: 1,2…”