Helium in chirped laser fields as a time-asymmetric atomic switch

0434945 - ÚFCH JH 2015 RIV US eng J - Journal Article
Kaprálová-Žďánská, Petra Ruth - Moiseyev, N.
Helium in chirped laser fields as a time-asymmetric atomic switch.
Journal of Chemical Physics. Roč. 141, č. 1 (2014), s. 014307. ISSN 0021-9606. E-ISSN 1089-7690
R&D Projects: GA ČR GAP205/11/0571
Institutional support: RVO:61388955
Keywords : Atom lasers * Laser pulses * Helium
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 2.952, year: 2014

Tuning the laser parameters exceptional points in the spectrum of the dressed laser helium atom are obtained. The weak linearly polarized laser couples the ground state and the doubly excited P-states of helium. We show here that for specific chirped laser pulses that encircle an exceptional point one can get the time-asymmetric phenomenon, where for a negative chirped laser pulse the ground state is transformed into the doubly excited auto-ionization state, while for a positive chirped laser pulse the resonance state is not populated and the neutral helium atoms remains in the ground state as the laser pulse is turned off. Moreover, we show that the results are very sensitive to the closed contour we choose. This time-asymmetric state exchange phenomenon can be considered as a time-asymmetric atomic switch. The optimal time-asymmetric switch is obtained when the closed loop that encircles the exceptional point is large, while for the smallest loops, the time-asymmetric phenomenon does not take place. A systematic way for studying the effect of the chosen closed contour that encircles the exceptional point on the time-asymmetric phenomenon is proposed. (C) 2014 AIP Publishing LLC.
Permanent Link: http://hdl.handle.net/11104/0238888