Optics and Spectroscopy

Spectroscopic study of the formation of excited strontium ions upon interaction of electrons with metastable atoms

І. І. Shafranyosh, T. A. Snegurskaya

Published Jul 1, 2006• 0 citations

Abstract

The interaction of electrons with metastable Sr atoms, as a result of which the latter are simultaneously ionized and excited, is investigated experimentally. The magnitudes of the interaction cross sections (reaching ≈5 × 10−20 m2 for the 52 S 1/2-32 P 3/2 transition in Sr II) and their energy dependences are determined. Possible mechanisms of this interaction are discussed.

DOI: 10.1134/s0030400x06070149

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Optics and Spectroscopy

Spectroscopic study of the formation of excited strontium ions upon interaction of electrons with metastable atoms

І. І. Shafranyosh, T. A. Snegurskaya

Published Jul 1, 2006• 0 citations

Publisher

Abstract

DOI: 10.1134/s0030400x06070149

Related papers

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The relative optical excitation functions and polarizations of the Sr resonance line (4607 \AA{}) and of the

{\mathrm{Sr}}^{+}

resonance lines (4078 and 4216 \AA{}) have been measured, using crossed electron and strontium-atom beams, for electron energies from the excitation thresholds to 1497 eV. The electron-beam energy resolution was \ensuremath{\sim} 0.22 eV for energies below 13 eV, and the atom beam was optically thin. The excitation functions of the ionic lines were measured relative to that of the atomic resonance line at fixed energies near the maxima of the excitation functions. Using spontaneous-emission branching ratios, this yields the ratios of total excitation cross sections for the atomic and ionic resonance levels (including cascades). The Sr

5^{1}P

excitation function has been normalized to Born theory taking account of cascade at 1497 eV, where the energy dependence of the excitation function has converged to the theoretical behavior. The resulting normalized cross sections have been compared with available theoretical calculations and other measurements. The 4607-\AA{} polarization function is consistent with the theoretical threshold limit within experimental uncertainity.

{}^{1}

{P}_{1}

resonance level, we show that a pool of metastable population is created, allowing an efficient heating of the medium by superelastic collisions with seed electrons, and a strong final ionization is achieved. When the laser source excites the 5s10s 7thinsp

{;}^{1}

{S}_{0}

Rydberg level, superelastic collisions do not occur and a drastic change in the population behavior is observed. In both cases the dynamics of the energy transfer towards the plasma is detailed.

{\mathrm{Sr}}^{+}

species. The collision cross sections associated with these reactions are studied as functions of applied laser frequency and power density. The largest cross section induced is equal to ${10}^{\ensuremath{-}16}$

{\mathrm{cm}}^{2}

, obtained at a power density of 2\ifmmode\times\else\texttimes\fi{}

{10}^{9}

{\mathrm{cm}}^{2}

. Differences in experimental results associated with the two reactions are explained qualitatively by an examination of the potential curves of the Ca

{\mathrm{Sr}}^{+}

quasimolecule.