Journal of Chemical Physics 936, 3787-3801
Sept. 15, 1990

Optical Absorption Spectroscopy of Sodium Clusters as Measured by Collinear Molecular Beam Photodepletion

C. R. Chris Wang, Stuart Pollack, Douglas Cameron and Manfred M. Kappes
Department of Chemistry, Northwestern University, Evanston, Illinois 60208

Reflections of blue laser light at the entrance to the detection chamber. This is the port where photodepletion light enters collinear to the molecular beam. The perspective here is looking into the rightmost port on the image of the machine below.


Collinear molecular beam photodepletion was used to obtain particle specific electronic absorption information for Na3, Na4, and Na8 in a wavelength range from 370-835 nm. We critically discuss the experimental method used and the deconvolution procedure applied to the resulting data to yield absolute absorption cross sections. The spectra contain much information on the cluster-size-dependent transition from molecular to bulk-like optical response and are interpreted in terms of various computational approaches ranging from classical electrostatic to ab initio large scale configuration interaction.


Experimental Setup

Experimental setup

Cluster beams are generated by supersonic expansion of sodium vapor from the oven source on the left of the leftmost chamber. The beam traverses liquid nitrogen cooled collimators in the left chamber and enters the detector chamber on the right where cluster densities are determined by one-photon ionization using a filtered arc lamp (foreground) focused into the ion source of a quadrupole mass spectrometer (top). Simultaneously, a tunable nanosecond pulsed laser beam is directed through a heated window on the right (and in image above). This is collinear with but counter propagating to the cluster beam.

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