| Literature DB >> 25415905 |
M Žitnik1, A Mihelič2, K Bučar2, M Kavčič2, J-E Rubensson3, M Svanquist3, J Söderström3, R Feifel4, C Såthe5, Y Ovcharenko6, V Lyamayev7, T Mazza8, M Meyer8, M Simon9, L Journel9, J Lüning9, O Plekan10, M Coreno10, M Devetta10, M Di Fraia11, P Finetti10, R Richter10, C Grazioli10, K C Prince12, C Callegari10.
Abstract
Seeded free electron lasers theoretically have the intensity, tunability, and resolution required for multiphoton spectroscopy of atomic and molecular species. Using the seeded free electron laser FERMI and a novel detection scheme, we have revealed the two-photon excitation spectra of dipole-forbidden doubly excited states in helium. The spectral profiles of the lowest (-1,0)(+1) (1)S(e) and (0,1)(0) (1)D(e) resonances display energy shifts in the meV range that depend on the pulse intensity. The results are explained by an effective two-level model based on calculated Rabi frequencies and decay rates.Entities:
Year: 2014 PMID： 25415905 DOI： 10.1103/PhysRevLett.113.193201
Source DB: PubMed Journal: Phys Rev Lett ISSN： 0031-9007 Impact factor: 9.161