Observation of Triplet Doubly Excited States in Single Photon Excitation from Ground State Helium

F. Penent; P. Lablanquie; R. I. Hall; M. Žitnik; K. Bučar; S. Stranges; R. Richter; M. Alagia; P. Hammond; J. G. Lambourne

doi:10.1103/PhysRevLett.86.2758

Observation of Triplet Doubly Excited States in Single Photon Excitation from Ground State Helium

F. Penent, P. Lablanquie, R. I. Hall, M. Žitnik, K. Bučar, S. Stranges, R. Richter, M. Alagia, P. Hammond, and J. G. Lambourne

Phys. Rev. Lett. 86, 2758 – Published 26 March 2001

Abstract

We have observed, for the first time, $LS$ -forbidden triplet doubly excited states, in single photon excitation of ground state helium, below the second ionization threshold. These states are identified as ${}^{3}D^{o}$ and ${}^{3}P^{o}$ and their excitation is due to spin-orbit interaction that mixes them with the optically allowed ${}^{1}P^{o}$ states. This observation is possible due to the very high efficiency in detecting metastable atoms created after the fluorescence decay of the doubly excited states, and the new capabilities of third generation synchrotron vacuum ultraviolet sources with high resolution beam lines.

Received 25 October 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.2758

Authors & Affiliations

F. Penent^1,*, P. Lablanquie², R. I. Hall¹, M. Žitnik³, K. Bučar³, S. Stranges⁴, R. Richter⁵, M. Alagia⁶, P. Hammond⁷, and J. G. Lambourne⁸

¹DIAM, Université P. & M. Curie, 75252 Paris Cedex 05, France
²LURE, Centre Universitaire Paris-Sud, 91898 Orsay, France
³J. Stefan Institute, 1000 Ljubljana, Slovenia
⁴Dipartimento di Chimica, Universitá di Roma “La Sapienza” and INFM Unit, 00185 Rome, Italy
⁵Sincrotrone Trieste, 34012 Trieste, Italy
⁶INFM-TASC, 34012 Trieste, Italy
⁷Department of Physics, University of Western Australia, Nedlands WA6907, Australia
⁸Department of Physics & Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom