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Phys. Rev. Lett. 78, 4371 - 4374 (1997)

Discrete Visible Luminescence of Helium Atoms and Molecules Desorbing from Helium Clusters: The Role of Electronic, Vibrational, and Rotational Energy Transfer

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K. von Haeften1, A. R. B. de Castro3, M. Joppien2, L. Moussavizadeh2, R. von Pietrowski1, and T. Möller1
1Hamburger Synchrotronstrahlungslabor HASYLAB and Deutsches Elektronen Synchroton DESY, Hamburg, Notkestr. 85, 22603 Hamburg, Germany
2II. Institute für Experimentalphysik, Universität Hamburg, Germany
3Laboratorio National de Luz Sincrotron, Campinas 13081-90, Brazil

Received 24 March 1997

Discrete visible and near-infrared luminescence of a beam of photoexcited helium clusters is reported. The emission lines are attributed to free helium atoms and molecules desorbing from clusters in electronically excited states. Depending on the excitation energy, various atomic and molecular singlet and triplet states are involved in the relaxation process. With increasing cluster size the intensity of molecular transitions becomes dominant. The temperature of ejected molecules could be estimated to Tvib∼2500 K and Trot∼450 K and is much higher than that of the cluster itself.


©1997 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevLett.78.4371
DOI: 10.1103/PhysRevLett.78.4371
PACS: 36.40.Mr, 33.50.Dq, 36.40.Qv

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