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Issue 42, 2011
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A cryogenic beam of refractory, chemically reactive molecules with expansion cooling

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Cryogenically cooled buffer gas beam sources of the molecule thorium monoxide (ThO) are optimized and characterized. Both helium and neon buffer gas sources are shown to produce ThO beams with high flux, low divergence, low forward velocity, and cold internal temperature for a variety of stagnation densities and nozzle diameters. The beam operates with a buffer gas stagnation density of ∼1015–1016 cm−3 (Reynolds number ∼1–100), resulting in expansion cooling of the internal temperature of the ThO to as low as 2 K. For the neon (helium) based source, this represents cooling by a factor of about 10 (2) from the initial nozzle temperature of about 20 K (4 K). These sources deliver ∼1011ThO molecules in a single quantum state within a 1–3 ms long pulse at 10 Hz repetition rate. Under conditions optimized for a future precision spectroscopy application [A. C. Vutha et al., J. Phys. B: At., Mol. Opt. Phys., 2010, 43, 074007], the neon-based beam has the following characteristics: forward velocity of 170 m s−1, internal temperature of 3.4 K, and brightness of 3 × 1011 ground state molecules per steradian per pulse. Compared to typical supersonic sources, the relatively low stagnation density of this source and the fact that the cooling mechanism relies only on collisions with an inert buffer gas make it widely applicable to many atomic and molecular species, including those which are chemically reactive, such as ThO.

Graphical abstract: A cryogenic beam of refractory, chemically reactive molecules with expansion cooling

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Publication details

The article was received on 24 Mar 2011, accepted on 27 May 2011 and first published on 22 Jun 2011

Article type: Paper
DOI: 10.1039/C1CP20901A
Citation: Phys. Chem. Chem. Phys., 2011,13, 18976-18985
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    A cryogenic beam of refractory, chemically reactive molecules with expansion cooling

    N. R. Hutzler, M. F. Parsons, Y. V. Gurevich, P. W. Hess, E. Petrik, B. Spaun, A. C. Vutha, D. DeMille, G. Gabrielse and J. M. Doyle, Phys. Chem. Chem. Phys., 2011, 13, 18976
    DOI: 10.1039/C1CP20901A

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