New Data on Autoionizing States of Ne Induced by Low-Energy Electrons from 45 to 64 eV

The lowest single and doubly excited autoionizing states of neon have been studied using a non-monochromatic electron beam and a high-resolution electrostatic analyzer at incident electron energies from 43.37 to 202 (±0.4) eV at three ejection angles, 40°, 90° and 130°. The 2s2p63s(3,1S) and 2s2p63p(3,1P) as well as the 2p43s3p doubly excited states have been observed and their energy determined. The influence of the PCI effect in the energy region of the 2s2p63s(3,1S) states has been investigated. New features in the ejected electron spectra in the low kinetic energy region 3–20 eV at 202 eV incident energy have been observed and assigned

The Auger spectra in argon induced by electron impact – new measurements with high resolution

The Auger spectrum of argon in the kinetic energy region (135–235 eV) has been measured using a non-monochromatic electron beam (incident energy from 313 to 2019 eV) at two ejection angles of 60° and 90° with a high resolution electrostatic analyzer. The electron impact energies of 313 and 323 eV have been used in order to disentangle the contribution of the ionization and decay of the 2s state. The systematic analysis of the measured spectra shows the dominance of the Coster-Kronig transitions from the 2s ionization in the energy region 135–159 eV and 208–235 eV, while the Auger transitions from the 2p ionization are dominant in the energy region 160–208 eV. The high resolution of the present work led to the observation of a certain number of new features in two energy regions 135–159 and 208–235 eV, respectively. Recent literature data on the cascade Auger processes and threshold formation of Ar2+ satellite states allow the assignment of some of them, while other have been left without assignments. The influence of the PCI effect on the line-shape, width and energy position of the features in the kinetic energy region 200–208 eV has been also investigated and the PCI shift versus excess energy above threshold compared with previous data and theoretical predictions

Energy and angular analysis of ejected electrons (6–26 eV) from the autoionization regions of argon at incident electron energies 505 and 2018 eV

High resolution ejected electron spectroscopy has been used to investigate a large number of Ar autoionizing states producing ejected electrons in the energy range from 6 to 26 eV at impact electron energies of 505 and 2018 eV and ejection angles of 40°, 90° and 130°. The full energy range has been divided into three regions which were analyzed separately. In the first one (6–9 eV) the obtained features are identified as the decay of the Ar2+(1D) at 45.11 eV. In the second one (9–14 eV) all features are identified as due to the decay of excited states formed by the excitation of 3s electrons to ns, np and nd subshells. The most prominent features are those arising from the excitation of 3s to nd(3,1D). In this series the 3s3p63d(1D) state with FWHM of 0.040 eV is used as the calibration point for all measured spectra. In the third energy region (14–26 eV) a large number of features is observed. Most of them are identified as the decay of excited states of the type 3s3p5nl and 3s23p4nln′l′

Singly and doubly excited states in ejected electron spectra of neon at high incident electron energies

Ejected electron spectroscopy has been used to study singly and doubly excited states of neon at constant incident electron energies between 505 and 2018 eV and ejection angles from 10° to 130° with high resolution in ejected energy range from 12 to 46 eV. The full ejected electron energy range has been studied at two extreme incidence energies and three ejected angles, namely 40°, 90° and 130°. The low energy region (12 to 21.5 eV) has been investigated at 505 eV over the full angular range and at 90° at six incident energies from 505 to 2018 eV. The features in the ejected electron spectra have been attributed to the autoionisation of Ne+ (2s2p6nl) excited states and Ne (2s2p5nln′l′ and 2s22p4nln′l′) double excited autionising states. Lower energy ejected electrons arise from simultaneous excitation of s and p electrons above the second ionisation potential (62.53 eV) while higher energy ejected electrons are coming from singly and doubly excited states. The high resolution and high sensitivity allowed us to see separated singlet from triplet states at high incident energies. Comparison with previous works gives a good agreement in energy positions of measured features. At the highest ejected electron energies only the features coming from double excitation are present, but with very low intensities in the spectra due to the small cross sections and high background. New resonances are found whose classification needs new experimental and theoretical investigations

Electron Impact Induced Fragmentation of N2H+ and N2D+

Electron impact dissociation of protonated and deuterated nitrogen ions has been studied using a crossed beams apparatus. Absolute cross sections for dissociation channels producing N+ and NH+, respectively, are presented. The observations of subthreshold signals in these measurements indicate the presence of ro-vibrationally and possibly electronically excited states in the parent ions. Comparisons with other measurements are given

Absolute cross sections and kinetic energy release distributions for electron-impact dissociative excitation and ionization of NeD+

Absolute cross sections for electron impact dissociative excitation and ionization of NeD+ leading to the formation of singly and multiply charged products (D+, Ne+, Ne2+ and Ne3+) are reported, in the energy range from their respective thresholds to 2.5 keV. The animated crossed-beams method is used. For singly charged fragments, absolute cross sections are obtained separately for dissociative excitation and for dissociative ionization. Dissociative excitation is seen to be restricted to the low-energy range (<300 eV) and the D+ formation dominates over the Ne+ one. At the maximum (around 35 eV), absolute cross sections for dissociative excitation are found to be (3.6 +/- 0.8) x 10(-17) cm(2) and (6.3 +/- 1.4) x 10(-17) cm(2) for Ne+ and D+, respectively; the corresponding appearance energies are (9.1 +/- 0.5) eV and (10.0 +/- 0.5) eV. The absolute cross section for dissociative ionization (Ne++D+ formation) is found to be (7.1 +/- 1.4) x 10(-17) cm(2), around 155 eV, and the threshold energy is (26.8 +/- 0.5) eV. For multiply charged products, absolute cross sections are found, around the maximum, to be (5.4 +/- 0.5) x 10(-18) cm(2) and (18.2 +/- 2.6) x 10(-20) cm(2) for Ne2+ and Ne3+, respectively; the corresponding thresholds are (53.1 +/- 1.0) eV and (132 +/- 5) eV. Kinetic energy release distributions are determined for each detected ionic product. The presented potential energy curves correspond to dissociation channels, which are significant for the discussion of present results. At fixed electron energy, the cross sections for the various ionization channels are seen to decrease exponentially with the potential energy of each dissociated ion pair

Absolute cross sections and kinetic energy release for doubly and triply charged fragments produced by electron impact on CO+

Absolute cross sections for electron impact ionization of CO+ leading to the formation of doubly and triply charged products (CO2+, C2+ and O2+, C3+ and O3+) are reported in the energy range from their respective thresholds to 2500 eV. Around the maximum, cross section values are found to be ( 13.36 +/- 0.56) x 10(-18) cm(2), ( 5.58 +/- 0.55) x 10(-18) cm(2) and (1.37 +/- 0.14) x 10(-18) cm(2) for CO2+, C2+ and O2+, respectively, and (28.3 +/- 7.0) x 10(-21) cm(2) and (2.4 +/- 0.7) x 10(-21) cm(2) for C3+ and O3+, respectively. The analysis of ionic product velocity distributions, obtained by means of a crossed electron-ion beam set-up, allows the determination of the kinetic energy release distributions. They are seen to extend from 0 to 50 eV both for C2+ and O2+. The mean kinetic energy releases for C3+ and O3+ are found to be 33 +/- 5 eV and 39 +/- 9 eV, respectively. The cross sections are seen to depend exponentially on the potential energy of each dissociated ion pair. The total single CO+ ionization cross section calculated by application of the Deutsch-Mark ( DM) formalism is found to be in good agreement with the experimental results

Intense-laser-field ionization of molecular hydrogen in the tunneling regime and its effect on the vibrational excitation of H2+.

H2 molecules were ionized by Ti:sapphire (45 fs, 800 nm) and Nd-doped yttrium aluminum garnet lasers (6 ns, 1064 nm). The relative populations of the vibrational levels of the H+2 ions were determined and found to be concentrated in the lowest vibrational levels. Tunneling ionization calculations with exact field-modified potential curves reproduce the experimental results. The reason for the departure from conventional Franck-Condon-like distributions is the rapid variation of the ionization rate with internuclear distance