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walhoutI spent my 2002-2003 sabbatical year in the metastable-helium group headed by C. Cohen-Tannoudji and M. Leduc in the Laboratoire Kastler Brossel of the Ecole Normale Supérieure, Paris.   Bose-Einstein condensation with metastable helium had already been demonstrated by then, and the group was beginning to shine near-resonant laser light into their trapped sample in an effort to excite bound molecular states of helium.  When this attempt at "photoassociation" (PA) of ultracold helium atoms gave its first clear signs of success in the form of resonant trap loss, and the group found itself with a twofold aim:  experimental characterization of the PA spectrum and theoretical modeling of the newly observed molecular resonances.  A delightfully energetic graduate student named Jérémie Léonard (now at Université de Strasbourg) undertook both aspects of the work as his Ph.D. thesis project.   It was my privilege to be part of his supporting cast, and to work with many other students, senior researchers, visiting scientists, and collaborators at ENS. The details of our investigations can be found in the references listed below.

--M. Walhout

Part of M.W.'s travel expenses were covered by the National Science Foundation (Grant NSF-PHYS-0140135).



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Collaborators in the LKB/ENS heliumphotoassociation heliumproject:

     Jérémie Léonard, Tobias Mueller, Steven Moal, Maximilien Portier

Group Leaders:
     Michèle Leduc, Claude Cohen-Tannoudji

     Allard Mosk (Twente), Peter van der Straten (Utrecht)

Visiting Researchers:
     C.S. Unnikrishnan, Umakant Rapol, Jae-Wan Kim, Matt Walhout


M. Walhout, J. Léonard,  M. Leduc, "Exotic helium dimers:  A giant comes out of the cold," Europhysics News, Vol. 36, p. 86-88 (May/June 2005).

J. Léonard, A. P. Mosk, M. Walhout, M. Leduc, M. van Rijnbach, D. Nehari and P. van der Straten, "Rotationally induced Penning ionization of ultracold photoassociated helium dimers," Europhys. Lett., 70 (2), pp. 190-196 (2005)

J. Kim, U.D. Rapol, S. Moal, J. Léonard, M. Walhout, M. Leduc, "Photoassociation experiments with ultracold metastable helium," European Physical Journal D 31, 227-237 (November 2004).

M. Leduc, J. Léonard, M. Walhout, "Des dimères géants avec des atomes d'hélium très excités...mais ultra-froids," Bulletin de la Société Française de Physique 145, p. 4 (July-August 2004).

J. Léonard, A.P. Mosk, M. Walhout, P. van der Straten, M. Leduc, and C. Cohen-Tannoudji, "Analysis of photoassociation spectra for giant helium dimers", Physical Review A, 69, 032702, 2004.

M. Leduc, M. Portier, J. Léonard, M. Walhout, F. Masnou-Seeuws, K. Willner, A. Mosk, "Photoassociation spectroscopy of ultracold metastable helium atoms: numerical analysis," in Laser Spectroscopy 16, Proceedings of the 16th International Conference on Laser Spectroscopy, Eds P.Hannaford, H.A. Bachor, K.G.Baldwin, A.I.Sidorov, (World Scientific, Palm Cove, Australia, July 2003).

J. Léonard, M. Walhout, A.P. Mosk, T. Mueller, M. Leduc, and C. Cohen-Tannoudji, "Giant Helium Dimers Produced by Photoassociation of Ultracold Metastable Atoms," Phys. Rev. Lett. 91, 073203 (15 August, 2003).