Light-induced states in attosecond transient absorption spectra of laser-dressed helium

Shaohao Chen, M. Justine Bell, Annelise R. Beck, Hiroki Mashiko, Mengxi Wu, Adrian N. Pfeiffer, Mette B. Gaarde, Daniel M. Neumark, Stephen R. Leone, and Kenneth J. Schafer

Phys. Rev. A 86, 063408 – Published 17 December 2012

Abstract

Laser-dressed absorption in atomic helium is studied, both theoretically and experimentally, by transient absorption spectroscopy using isolated 400-as pulses centered at 22 eV and 12-fs near-infrared (NIR) pulses with 780-nm central wavelength. Multiple features in the helium singly excited bound-state spectrum are observed only when the NIR and attosecond pulses are overlapped in time. Theoretical analysis indicates that these light-induced structures (LISs) are the intermediate states in resonant, second-order processes that transfer population to multiple dipole forbidden states. The use of broadband, coherent extreme ultraviolet (XUV) radiation allows observation of these LISs without specifically tuning to a two-photon resonance, as would be required with narrowband XUV light. The strength and position of the LISs depend strongly on the NIR intensity and the pump-probe delay.

Received 5 September 2012

DOI:https://doi.org/10.1103/PhysRevA.86.063408

Authors & Affiliations

Shaohao Chen^1,*, M. Justine Bell^2,3,*, Annelise R. Beck^2,3, Hiroki Mashiko², Mengxi Wu¹, Adrian N. Pfeiffer^2,3, Mette B. Gaarde¹, Daniel M. Neumark^2,3, Stephen R. Leone^2,3,4, and Kenneth J. Schafer¹

¹Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
²Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
³Department of Chemistry, University of California, Berkeley, California 94720, USA
⁴Department of Physics, University of California, Berkeley, California 94720, USA

^*These authors contributed equally to this work.

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Vol. 86, Iss. 6 — December 2012

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