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arXiv:0710.3316 · Physical Review A

Internal-state thermometry by depletion spectroscopy in a cold guided beam of formaldehyde

M. Motsch, Markus Schenk, L. D. van Buuren, Martin Zeppenfeld, Pepijn W. H. Pinkse, Gerhard Rempe

Published Dec 20, 2007• 24 citations
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Abstract

We present measurements of the internal state distribution of electrostatically guided formaldehyde. Upon excitation with continuous tunable ultraviolet laser light the molecules dissociate, leading to a decrease in the molecular flux. The population of individual guided states is measured by addressing transitions originating from them. The measured populations of selected states show good agreement with theoretical calculations for different temperatures of the molecule source. The purity of the guided beam as deduced from the entropy of the guided sample using a source temperature of $150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ corresponds to that of a thermal ensemble with a temperature of about $30\phantom{\rule{0.3em}{0ex}}\mathrm{K}$.

DOI
10.1103/physreva.76.061402

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We describe the combination of buffer-gas cooling with electrostatic velocity filtering to produce a high-flux continuous guided beam of internally cold and slow polar molecules. In a previous paper (L.D. van Buuren et al., Phys. Rev. Lett., 2009, 102, 033001) we presented results on density and state purity for guided beams of ammonia and formaldehyde using an optimized set-up. Here we describe in more detail the technical aspects of the cryogenic source, its operation, and the optimization experiments that we performed to obtain the best performance. The versatility of the source is demonstrated by the production of guided beams of different molecular species.
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