High resolution multiphoton spectroscopy by a tunable free-electron-laser light.

Summary, in English

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.

• Author: M Zitnik; A Mihelič; K Bučar; M Kavčič; J-E Rubensson; M Svanquist; J Söderström; R Feifel; Conny Såthe; Y Ovcharenko; V Lyamayev; T Mazza; M Meyer; M Simon; L Journel; J Lüning; O Plekan; M Coreno; M Devetta; M Di Fraia; P Finetti; R Richter; C Grazioli; K C Prince; C Callegari
• Department/s: MAX IV Laboratory
• Publishing year: 2014
• Language: English
• Publication/Series: Physical Review Letters
• Volume: 113
• Issue: 19
• Links: http://dx.doi.org/10.1103/PhysRevLett.113.193201
• Document type: Journal article
• Publisher: American Physical Society
• Topic: Natural Sciences; Physical Sciences
• Status: Published
• ISBN/ISSN/Other: ISSN: 1079-7114