title: Size and shape dependent photoluminescence and excited state decay rates of diamondoids.
abstract: We present photoluminescence spectra and excited state decay rates of a series of diamondoids, which represent molecular structural analogues to hydrogen-passivated bulk diamond. Specific isomers of the five smallest diamondoids (adamantane-pentamantane) have been brought into the gas phase and irradiated with synchrotron radiation. All investigated compounds show intrinsic photoluminescence in the ultraviolet spectral region. The emission spectra exhibit pronounced vibrational fine structure which is analyzed using quantum chemical calculations. We show that the geometrical relaxation of the first excited state of adamantane, exhibiting Rydberg character, leads to the loss of Td symmetry. The luminescence of adamantane is attributed to a transition from the delocalized first excited state into different vibrational modes of the electronic ground state. Similar geometrical changes of the excited state structure have also been identified in the other investigated diamondoids. The excited state decay rates show a clear dependence on the size of the diamondoid, but are independent of the particle geometry, further indicating a loss of particle symmetry upon electronic excitation.
authors.affiliation: Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany. robert.richter@tu-berlin.de.
authors.forename: Robert
authors.initials: R
authors.lastname: Richter
authors.forename: David
authors.initials: D
authors.lastname: Wolter
authors.forename: Tobias
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authors.lastname: Zimmermann
authors.forename: Lasse
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authors.lastname: Landt
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authors.lastname: Knecht
authors.forename: Christoph
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authors.lastname: Heidrich
authors.forename: Andrea
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authors.lastname: Merli
authors.forename: Otto
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authors.lastname: Dopfer
authors.forename: Philipp
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authors.lastname: Reiss
authors.forename: Arno
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authors.lastname: Ehresmann
authors.forename: Jens
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authors.lastname: Petersen
authors.forename: Jeremy E
authors.initials: JE
authors.lastname: Dahl
authors.forename: Robert M K
authors.initials: RM
authors.lastname: Carlson
authors.forename: Christoph
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authors.lastname: Bostedt
authors.forename: Thomas
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authors.lastname: Möller
authors.forename: Roland
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authors.lastname: Mitric
authors.forename: Torbjörn
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authors.lastname: Rander