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arXiv · 1402.3128

Probing dipole-forbidden autoionizing states by isolated attosecond pulses

Wei-Chun Chu·Toru Morishita·C. D. Lin
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Abstract

We propose a general technique to retrieve the information of dipole-forbidden resonances in the autoionizing region. In the simulation, a helium atom is pumped by an isolated attosecond pulse in the extreme ultraviolet (EUV) combined with a few-femtosecond laser pulse. The excited wave packet consists of the $^1S$, $^1P$, and $^1D$ states, including the background continua, near the $2s2p(^1P)$ doubly excited state. The resultant electron spectra with various laser intensities and time delays between the EUV and laser pulses are obtained by a multilevel model and an ab initio time-dependent Schrödinger equation calculation. By taking the ab initio calculation as a "virtual measurement", the dipole-forbidden resonances are characterized by the multilevel model. We found that in contrast to the common assumption, the nonresonant coupling between the continua plays a significant role in the time-delayed electron spectra, which shows the correlation effect between photoelectrons before they leave the core. This technique takes the advantages of ultrashort pulses uniquely and would be a timely test for the current attosecond technology.

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Wei-Chun Chu, Toru Morishita, C. D. Lin. 2014-03-27. Probing dipole-forbidden autoionizing states by isolated attosecond pulses. https://doi.org/10.1103/physreva.89.033427

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