Tunable diode laser spectroscopy of helium clusters

被引：0
作者：
A.R.W. Mc Kellar
机构：
[1] National Research Council of Canada,Steacie Institute for Molecular Sciences
来源：
Applied Physics B | 2008年 / 90卷
关键词：
Cluster Size; Probe Molecule; Helium Cluster; Backing Pressure; Helium Nanodroplets;
D O I：
暂无
中图分类号：
学科分类号：
摘要：
Helium clusters, HeN-X, containing a probe molecule, X, are studied by infrared spectroscopy for the size range N≈1∼100. Spectra are observed using a supersonic jet expansion and a tunable diode laser source operating in a rapid-scan (sweep integration) mode. The pulsed jet uses a dilute gas mixture of the probe molecule in helium, with relatively high backing pressures (5–50 bar), and a cooled (80–295 K) nozzle. Sensitivity is enhanced by multi-passing the laser beam through the jet with a toroidal mirror system. The clusters are larger than van der Waals dimers and trimers, but smaller than those encountered in the field of helium nanodroplets (N≈103–105). Furthermore, individual cluster sizes are resolved here, but not with nanodroplets, and infrared absorption is detected directly (change in transmitted laser intensity), rather than indirectly (change in cluster fragmentation). Trends in the spectra are described for five probe molecules, X=CO, SiH4, OCS, N2O, and CO2. Superfluid effects dominate for clusters larger than N≈8. Notable results include the unexpected observation of broad oscillations in the effective rotational constants as a function of cluster size.
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页码：213 / 225
页数：12
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