Experimental and theoretical cross sections for photoionization of metastable atoms near threshold

Abstract

Using high-resolution laser photoelectron spectrometry we have determined for the first time absolute cross sections and the electron angular distribution parameter for one-photon ionization of metastable atoms to the resolved ion states near threshold as well as the -parameter for metastable atoms at , 257.25 nm. For comparison with present and future experimental data we have calculated partial cross sections and -parameters for photoionization of , and of the analogous alkali atom over the photoelectron energy range 0 - 10 eV. We have used both a term-dependent Hartree - Fock approach and a configuration-interaction method involving Pauli - Fock atomic orbitals (CIPF); the latter was designed to take into account the important electron correlation effects which are found to be essential for obtaining good agreement between the theoretical and experimental results. .

Experimental and theoretical cross sections for photoionization of metastable Xe*. (6s 3 P 2, 3 P 0) atoms near threshold

“…The open shell nature of the Rg + [(m − 1)p 5 ] ion core leads, however, to specific properties of the rare gases such as series of prominent autoionization resonances between the two lowest ionization potentials 2 P 3/2 − 2 P 1/2 [1][2][3][4][5] and the presence of substantial admixture of d-valence character [6][7][8][9][10][11][12][13], which is especially strong for the Xe * (5p 5 6s J = 0) metastable level due to the proximity to the Xe * (5p 5 5dJ = 0) level [9][10][11][12][13]. The latter effects and the influence of electron correlations associated with virtual excitations of the core electrons [14][15][16][17][18][19] lead to the one photon excitation of nf Rydberg states besides np states and, On leave from: Rostov State University of Transport Communications, Rostov-on-Don, Russia correspondingly, cause the appearance of εf partial photoelectron waves besides εp waves in electric dipole single photoionization of Rg * , as described by the reactions:…”

Resonance and Threshold Phenomena in Low-Energy Electron Collisions with Molecules and Clusters

“…39 K(4s 1/2 , F ¼ 1, 2) atoms to the intermediate levels 40 Ar * (4p 3 D 3 ) or 39 K * (4p 3/2 , F 0 ¼ 2, 3) (quasi-stationary excited state population nearly 50%), is optimized in the sense that the cross-section for ionization of Ar * (4p 3 D 3 ) (Schohl et al, 1997) as well as for K * (4p 3/2 ) atoms (Petrov et al, 2000) is substantial (around 10 À21 m 2 ) and three to four orders of magnitude higher than that for ionization of metastable Ar * (4s 3 P 2 ) atoms (Kau et al, 1998;Petrov et al, 1999) or ground state K(4s) atoms (Sandner et al, 1981), respectively. We note that an analogous two-step photoionization scheme involving ground state Na(3s 1/2 ) atoms has been recently applied by Keil et al (1999) to study laser photoelectron attachment to vibrationally excited Na 2 molecules (see Section IV.B).…”

Ultrafast Interatomic Electronic Decay in Multiply Excited Clusters

“…(1) are known from the literature -the oscillator strength for the 3s → 2p transition in neon is 0.16 [13] and the photoionization cross section of Ne * (2p −1 3s) is about 0.18 Mb [14]. At the Ne 2 equilibrium distance of 3.1Å the decay width for the process is 0.24 meV, which implies a life time of about 2.8 ps.…”

“…In this case, Eqs. (2) can be easily solved and using the atomic data, σ 0 ≈ 273 Mb [13], σ 1 ≈ 0.18 Mb [14], and σ 2 ≈ 2 × 10 −49 cm 4 s [18], one obtains that in the Ne 1000 cluster after the pulse 991 atoms will be excited and only 3 will be ionized by a two-photon ionization. Since, as we saw, the ICD process is very efficient, one would expect that every pair of Ne * (2p −1 3s) will undergo ICD producing about 495 neon ions.…”