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Title: Branching ratios in the radiative decay of helium doubly excited states

Abstract

The doubly excited singlet states of He below the N=2 threshold may decay by autoionization or fluorescence. In the fluorescence decay channel, most decay cascades consist of emission of three photons, of which the first is a VUV photon, the second is in or near the visible range, and the last is another VUV photon. We have studied the fluorescence channel decay dynamics of the (2,0{sub n}) (2,1{sub n}) and (2,-1{sub n}) {sup 1}P, n=3-7, states by wavelength dispersed photon-induced fluorescence spectroscopy. We have detected the photons in the second step of the cascade and determined the branching ratios for the strongest lines in this step. From these data we are able to calculate the branching ratios of the first step in the cascade. The results are in good agreement with calculations of the main decay channels of the higher resonances, but about 20-30 % lower, and so we are able to describe quantitatively the whole fluorescence cascade of the above-mentioned doubly excited states.

Authors:
 [1];  [2];  [3];  [2];  [3];  [4]; ;  [5]
  1. CNR-IMIP, Area della Ricerca di Roma 1, Montelibretti (Rome), I-00016 (Italy)
  2. (Italy)
  3. Sincrotrone Trieste, in Area Science Park, I-34012 Basovizza (Trieste) (Italy)
  4. CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste (Italy)
  5. J. Stefan Institute, 1000 Ljubljana (Slovenia)
Publication Date:
OSTI Identifier:
20786501
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 72; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.72.052512; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOMS; AUTOIONIZATION; BRANCHING RATIO; EXCITED STATES; FAR ULTRAVIOLET RADIATION; FLUORESCENCE; FLUORESCENCE SPECTROSCOPY; HELIUM; PHOTONS; RADIATIVE DECAY; RESONANCE; WAVELENGTHS

Citation Formats

Coreno, M., CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste, Prince, K. C., CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste, Richter, R., De Simone, M., Bucar, K., and Zitnik, M. Branching ratios in the radiative decay of helium doubly excited states. United States: N. p., 2005. Web. doi:10.1103/PHYSREVA.72.0.
Coreno, M., CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste, Prince, K. C., CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste, Richter, R., De Simone, M., Bucar, K., & Zitnik, M. Branching ratios in the radiative decay of helium doubly excited states. United States. doi:10.1103/PHYSREVA.72.0.
Coreno, M., CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste, Prince, K. C., CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste, Richter, R., De Simone, M., Bucar, K., and Zitnik, M. Tue . "Branching ratios in the radiative decay of helium doubly excited states". United States. doi:10.1103/PHYSREVA.72.0.
@article{osti_20786501,
title = {Branching ratios in the radiative decay of helium doubly excited states},
author = {Coreno, M. and CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste and Prince, K. C. and CNR-Laboratori TASC-INFM, in Area Science Park, Loc. Basovizza, I-34012 Trieste and Richter, R. and De Simone, M. and Bucar, K. and Zitnik, M.},
abstractNote = {The doubly excited singlet states of He below the N=2 threshold may decay by autoionization or fluorescence. In the fluorescence decay channel, most decay cascades consist of emission of three photons, of which the first is a VUV photon, the second is in or near the visible range, and the last is another VUV photon. We have studied the fluorescence channel decay dynamics of the (2,0{sub n}) (2,1{sub n}) and (2,-1{sub n}) {sup 1}P, n=3-7, states by wavelength dispersed photon-induced fluorescence spectroscopy. We have detected the photons in the second step of the cascade and determined the branching ratios for the strongest lines in this step. From these data we are able to calculate the branching ratios of the first step in the cascade. The results are in good agreement with calculations of the main decay channels of the higher resonances, but about 20-30 % lower, and so we are able to describe quantitatively the whole fluorescence cascade of the above-mentioned doubly excited states.},
doi = {10.1103/PHYSREVA.72.0},
journal = {Physical Review. A},
number = 5,
volume = 72,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
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