Copper clusters ranging in size from 1 to 29 atoms have been prepared in a supersonic beam by laser vaporization of a rotating copper target rod within the throat of a pulsed supersonic nozzle using helium for the carrier gas. The clusters were cooled extensively in the supersonic expansion [T(translational) 1 to 4 K, T(rotational)=4 K, T(vibrational)=20 to 70 K]. These clusters were detected in the supersonic beam by laser photoionization with time-of-flight mass analysis. Using a number of fixed frequency outputs of an exciplex laser, the threshold behavior of the photoionization cross section was monitored as a function of cluster size. The 7.9 eV photon energy of the F2 excimer laser was found to be above the ionization potential of all clusters, and the photoion mass spectrum thus produced showed the copper cluster concentration in the beam to follow a monotonically decreasing function of cluster size. The 6.4 eV ArF exciplex laser photon energy was found to be above the photoionization threshold of clusters with three or more atoms in the case of odd-numbered clusters, but only for clusters with eight or more atoms for even-numbered clusters. Extending out to clusters as large as 29 atoms, laser photoionization at 6.4 eV produced a time-of-flight mass distribution with a pronounced even/odd alternation in cluster photoion intensity. This alternation in ionization threshold behavior was attributed to an even/odd alternation in the electronic structure of the copper clusters with the highest occupied molecular orbital (HOMO) of the even clusters being considerably more strongly bonding than it is in the clusters with an odd number of copper atoms. The 4.98 eV photon energy of the KrF exciplex laser was found to lie below the ionization threshold of all clusters in the 1 to 29 atom range. An extensive survey of the ultraviolet absorption spectrum of the copper dimer was also performed with this supersonic beam source. Resonance two-photon ionization (R2PI) with mass selective detection allowed the detection of five new electronic band systems in the region between 2690 and 3200 Å, for each of the three naturally occurring isotopic forms of Cu2. In the process of scanning the R2PI spectrum of these new electronic states, the ionization potential of the copper dimer was determined to be 7.894±0.015 eV.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSupersonic metal cluster beams: laser photoionization studies of copper cluster (Cu2)D. E. Powers, S. G. Hansen, M. E. Geusic, A. C. Puiu, J. B. Hopkins, T. G. Dietz, M. A. Duncan, P. R. R. Langridge-Smith, and R. E. SmalleyCite this: J. Phys. Chem. 1982, 86, 14, 2556–2560Publication Date (Print):July 1, 1982Publication History Published online1 May 2002Published inissue 1 July 1982https://pubs.acs.org/doi/10.1021/j100211a002https://doi.org/10.1021/j100211a002research-articleACS PublicationsRequest reuse permissionsArticle Views1114Altmetric-Citations251LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Ring-bound van der Waals complexes of the alkylbenzenes are studied.(AIP)

Cold beams of metal clusters are produced by combining a laser vaporization technique with pulsed supersonic nozzle technology. (AIP)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLaser production of jet-cooled radicals. Methoxy and methoxy-argonD. E. Powers, J. B. Hopkins, and R. E. SmalleyCite this: J. Phys. Chem. 1981, 85, 19, 2711–2713Publication Date (Print):September 1, 1981Publication History Published online1 May 2002Published inissue 1 September 1981https://pubs.acs.org/doi/10.1021/j150619a003https://doi.org/10.1021/j150619a003research-articleACS PublicationsRequest reuse permissionsArticle Views165Altmetric-Citations81LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Spectrally resolved fluorescence time decay measurements have been completed with nanosecond resolution on a series of n-alkylbenzenes laser excited into well-localized ring distortion vibrations in the S1 electronic state. Results indicate that those early members of the series which continue to exhibit some sharp, vibrationally unrelaxed emissions do so because they are intermediate case examples with inadequate density of states to permit dynamical relaxation on a nanosecond time scale. The longer chain, statistical limit molecules show a relaxed fluorescence pattern which displays no residual nanosecond time evolution. Intramolecular vibrational relaxation thus appears to proceed to an essentially complete randomization within a time period shorter than the excitation laser pulse.

Fluorescence excitation spectra have been recorded for the first 6000 cm−1 of the ultraviolet spectrum of h8- and d8-naphthalene cooled in a supersonic free jet. Measured profiles of vibronic bands in these spectra display a monotonically increasing width as a function of vibrational energy (Ev) in the excited electronic state. The high fluorescence quantum yield and relatively constant fluorescence lifetimes in these spectral regions require the measured line broadening to be assigned to intramolecular vibrational relaxation (IVR) within the excited electronic state. The rate of this IVR process as measured by the width of the broadened profiles increases smoothly from 9×1010 sec−1 at Ev=3068 cm−1 to 7×1011 sec−1 at Ev=5200 cm−1 for h8-naphthalene. Line profiles of d8-naphthalene in this same spectral region are found to be ∼50% wider.