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 Se1 and (0,1)0 De1 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.
High Resolution Multiphoton Spectroscopy by a Tunable Free-Electron-Laser Light / Žitnik, M.; Mihelič, A.; Bučar, K.; Kavčič, M.; Rubensson, J. E.; Svanquist, M.; Söderström, J.; Feifel, R.; Såthe, C.; Ovcharenko, Y.; Lyamayev, V.; Mazza, T.; Meyer, M.; Simon, M.; Journel, L.; Lüning, J.; Plekan, O.; Coreno, M.; Devetta, M.; DI FRAIA, Michele; Finetti, P.; Richter, R.; Grazioli, C.; Prince, K. . C.; Callegari, C.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 113:(2014), pp. 193201-193206. [10.1103/PhysRevLett.113.193201]
High Resolution Multiphoton Spectroscopy by a Tunable Free-Electron-Laser Light
DI FRAIA, MICHELE;
2014-01-01
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 Se1 and (0,1)0 De1 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.Pubblicazioni consigliate
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