The spectral stability of three guest molecules embedded in a quickly frozen n-tetradecane matrix has been investigated on a single-molecular level at liquid-helium temperature. In total, about... Show moreThe spectral stability of three guest molecules embedded in a quickly frozen n-tetradecane matrix has been investigated on a single-molecular level at liquid-helium temperature. In total, about 2500 spectral trajectories of 476 terrylene molecules, 328 dibenzanthanthrene molecules, and 252 pentacene molecules were recorded. Both line broadening and spectral jumps are analyzed and the latter are found to be mainly light induced. The spectral changes in essence reflect the dynamics of the host matrix and the differences between the guest molecules may be reduced to differences in their pumping cycles. (C) 2001 American Institute of Physics. Show less
We report the spectroscopic observation of single pentacene molecules in the matrices n-tetradecane and n-hexadecane, using a confocal microscope operating at liquid-helium temperatures. A maximum... Show moreWe report the spectroscopic observation of single pentacene molecules in the matrices n-tetradecane and n-hexadecane, using a confocal microscope operating at liquid-helium temperatures. A maximum detected photon emission rate of only 30 counts per second (cps) is found for pentacene in n-hexadecane and 160 cps for pentacene in n-tetradecane. For the latter system, the low count rate is shown to be caused by a high S-1 --> T-1 intersystem crossing yield of about 40% in combination with a triplet lifetime of 33 +/- 3 mu s. Pentacene molecules in this polycrystalline host are found to show little spectral diffusion on a timescale of seconds. (C) 2000 Elsevier Science B.V. All rights reserved. Show less
Brouwer, A.C.J.; Köhler, J.; Groenen, E.J.J.; Schmidt, J. 1996
Weak satellites in S-1<--S-0 excitation spectra of natural-abundance pentacene in p-terphenyl due to position-specific C-13 isotope shifts were observed. An assignment of these satellites to the... Show moreWeak satellites in S-1<--S-0 excitation spectra of natural-abundance pentacene in p-terphenyl due to position-specific C-13 isotope shifts were observed. An assignment of these satellites to the various carbon positions is derived. The extremely narrow inhomogeneous linewidth allowed selective excitation of pentacene molecules with C-13 in specific positions. Spectra of the magnetic-resonance transition between triplet sublevels of such ensembles, and of individual pentacene molecules showed position-specific C-13 hyperfine broadening. (C) 1996 American Institute of Physics. Show less
Köhler, J.; Brouwer, A.C.J.; Groenen, E.J.J.; Schmidt, J. 1996
Applying methods developed for single molecule spectroscopy to small ensembles, we have recorded high-resolution fluorescence-excitation spectra for pentacene in all substitutional sites of a p... Show moreApplying methods developed for single molecule spectroscopy to small ensembles, we have recorded high-resolution fluorescence-excitation spectra for pentacene in all substitutional sites of a p-terphenyl single crystal. The difference in intersystem crossing efficiency for pentacene molecules in the various substitutional sites is discussed on the basis of these spectra and data from optically detected magnetic resonance experiments. Show less
Meer, H. van der; Disselhorst, J.A.J.M.; Köhler, J.; Brouwer, A.C.J.; Groenen, E.J.J.; Schmidt, J. 1995
We describe an insert for optical and magnetic-resonance experiments on single molecules in a solid matrix at liquid-helium temperatures. The experimental arrangement allows in situ adjustment of... Show moreWe describe an insert for optical and magnetic-resonance experiments on single molecules in a solid matrix at liquid-helium temperatures. The experimental arrangement allows in situ adjustment of the focusing lens and of the sample. A parabolic mirror serves to collect the fluorescence emission and to direct the light onto a photodetector. Microwaves can be irradiated through a coil around the sample while a superconducting magnet provides the possibility of a stationary magnetic field. (C) 1995 American Institute of Physics. Show less
Köhler, J.; Brouwer, A.C.J.; Groenen, E.J.J.; Schmidt, J. 1995
Individual pentacene-d(14) molecules doped into a p-terphenyl-d(14) host crystal have been studied by optically detected electron paramagnetic resonance spectroscopy. The magnetic resonance... Show moreIndividual pentacene-d(14) molecules doped into a p-terphenyl-d(14) host crystal have been studied by optically detected electron paramagnetic resonance spectroscopy. The magnetic resonance transitions between the triplet sublevels of the pentacene molecule and the splitting of the resonance lines for a molecule that contains a carbon-13 nucleus have been observed in an edernal magnetic field. This splitting is caused by the hyperfine interaction of the triplet electron spin with the single carbon-13 nuclear spin. Show less
Köhler, J.; Brouwer, A.C.J.; Groenen, E.J.J.; Schmidt, J. 1994
We report the observation of the broadening of a magnetic-resonance transition between triplet sublevels of a single pentacene molecule owing to the interaction of the triplet electron spin with a... Show moreWe report the observation of the broadening of a magnetic-resonance transition between triplet sublevels of a single pentacene molecule owing to the interaction of the triplet electron spin with a single C-13 nuclear spin. Analysis of this broadening allows the assignment of particular features in the fluorescence-excitation spectrum to pentacene molecules containing C-13 isotopes in specific positions. Show less
THE introduction of optical detection methods for observing magnetic resonance transitions in metastable paramagnetic states1-4 has contributed enormously to our understanding of the properties of... Show moreTHE introduction of optical detection methods for observing magnetic resonance transitions in metastable paramagnetic states1-4 has contributed enormously to our understanding of the properties of photoexcited molecules in condensed phases. In such experiments the luminescence intensity is recorded as a function of the frequency of an applied microwave field. At resonance with transitions between sublevels of a metastable paramagnetic state, the lifetime of the metastable state is altered and a consequent change in the luminescence intensity is observed. Here we report the observation of such optically detected magnetic resonance transitions for the triplet state of a single pentacene molecule embedded in a p-terphenyl host crystal. This result has been obtained by combining the conventional optical detection technique for observing magnetic resonance transitions1-4 with the new single-molecule optical detection methods developed recently5,6. This observation opens the way for magnetic resonance studies in condensed phases with single-molecule sensitivity. Show less
