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Title: Evidence of the 2s2p({sup 1}P) doubly excited state in the harmonic generation spectrum of helium

Abstract

By solving the two-active-electron time-dependent Schroedinger equation in an intense, ultrashort laser field, we investigate evidence of electron correlations in the high-order harmonic generation spectrum of helium. As the frequency of the driving laser pulse varies from 4.6 to 6.6 eV, the 13th, 11th, and 9th harmonics sequentially become resonant with the transition between the ground state and the isolated 2s2p({sup 1}P) autoionizing state of helium, which dramatically enhances these harmonics and changes their profiles. When each of the 9th and 13th harmonics are in resonance with this autoionizing state, there is also a low-order multiphoton resonance with a Rydberg state, resulting in a particularly large enhancement of these harmonics relative to neighboring harmonics. When the 11th harmonic is in resonance with the 2s2p({sup 1}P) autoionizing state, the 13th harmonic is simultaneously in resonance with numerous higher-energy autoionizing states, resulting in a competition between these two harmonics for intensity. These results demonstrate that even electron correlations occurring over a narrow energy interval can have a significant effect on strong-field processes such as harmonic generation.

Authors:
;  [1]
  1. Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299 (United States)
Publication Date:
OSTI Identifier:
22051315
Resource Type:
Journal Article
Journal Name:
Physical Review. A
Additional Journal Information:
Journal Volume: 84; Journal Issue: 1; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1050-2947
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ELECTRON CORRELATION; ELECTRONS; EV RANGE 01-10; GROUND STATES; HARMONIC GENERATION; HARMONICS; HELIUM; LASER RADIATION; RESONANCE; RYDBERG STATES; SCHROEDINGER EQUATION; SPECTRA; TIME DEPENDENCE

Citation Formats

Ngoko Djiokap, J. M., and Starace, Anthony F. Evidence of the 2s2p({sup 1}P) doubly excited state in the harmonic generation spectrum of helium. United States: N. p., 2011. Web. doi:10.1103/PHYSREVA.84.013404.
Ngoko Djiokap, J. M., & Starace, Anthony F. Evidence of the 2s2p({sup 1}P) doubly excited state in the harmonic generation spectrum of helium. United States. doi:10.1103/PHYSREVA.84.013404.
Ngoko Djiokap, J. M., and Starace, Anthony F. Fri . "Evidence of the 2s2p({sup 1}P) doubly excited state in the harmonic generation spectrum of helium". United States. doi:10.1103/PHYSREVA.84.013404.
@article{osti_22051315,
title = {Evidence of the 2s2p({sup 1}P) doubly excited state in the harmonic generation spectrum of helium},
author = {Ngoko Djiokap, J. M. and Starace, Anthony F.},
abstractNote = {By solving the two-active-electron time-dependent Schroedinger equation in an intense, ultrashort laser field, we investigate evidence of electron correlations in the high-order harmonic generation spectrum of helium. As the frequency of the driving laser pulse varies from 4.6 to 6.6 eV, the 13th, 11th, and 9th harmonics sequentially become resonant with the transition between the ground state and the isolated 2s2p({sup 1}P) autoionizing state of helium, which dramatically enhances these harmonics and changes their profiles. When each of the 9th and 13th harmonics are in resonance with this autoionizing state, there is also a low-order multiphoton resonance with a Rydberg state, resulting in a particularly large enhancement of these harmonics relative to neighboring harmonics. When the 11th harmonic is in resonance with the 2s2p({sup 1}P) autoionizing state, the 13th harmonic is simultaneously in resonance with numerous higher-energy autoionizing states, resulting in a competition between these two harmonics for intensity. These results demonstrate that even electron correlations occurring over a narrow energy interval can have a significant effect on strong-field processes such as harmonic generation.},
doi = {10.1103/PHYSREVA.84.013404},
journal = {Physical Review. A},
issn = {1050-2947},
number = 1,
volume = 84,
place = {United States},
year = {2011},
month = {7}
}