We applied hydrostatic pressure to spectral holes burned into a resorufin doped ethanol/methanol glass. We found that the line shift is perfectly linear with pressure and showed a pronounced dependence on the burn frequency as predicted by theory [J. Chem. Phys. 90, 3274 (1989)]. We exploited the burn frequency dependence to determine the solvent shift of the dye probe and the compressibility of the alcohol glass used. On the other hand, the behavior of the hole width under pressure shows features not predicted by theory: The broadening is, like the line shift, dependent on the burn frequency within the inhomogeneous band, yet in a nonlinear fashion. We attribute the color effect in the pressure induced broadening of the hole to a breakdown of the Gaussian approximation.
Octatetraene can be photoisomerized even when it is incorporated in a low temperature n-hexane crystal. When this is done by irradiating the zero-phonon component of the S0→S1 origin band with a single frequency laser, very narrow (∼10 MHz) persistent holes can be burned. We have determined the effect of an externally applied electric field on these persistent holes and fit the observed data with a simple quantum mechanical model parameterized in the S0→S2 and S1→S2 transition dipoles and the magnitude of a molecular field intrinsic to the n-hexane site occupied by the octatetraene guest. The magnitude of the molecular field (∼106 V/cm) is consistent with only one of the three possible n-hexane sites that could have accommodated the octatetraene guest.
Articles you may be interested in A general nuclear magnetic resonance analysis of hetero-association of aromatic molecules in aqueous solutionWe present phosphorescence wavelength selected optically detected magnetic resonance (ODMR) experiments on some aromatic molecules in organic glasses. The change of the ODMR frequency and width as a function of phosphorescence wavelength is interpreted in terms of a spinless stochastic Hamiltonian which describes the interaction between the probe molecule and the solvent. It is shown that the phonons in the optical spectra have a significant influence on the parameters of the ODMR profile.120.
We investigate the triplet state of molecular aggregates of pseudoisocyanine iodide by emission, excitation, and optically detected magnetic resonance spectroscopy. The phosphorescence seems to stem entirely from aggregated species. It is enhanced by reabsorption processes. H and J aggregates can be distinguished by their different triplet energies and zero-field resonances. The spin-lattice relaxation does not play any significant role in the triplet dynamics up to temperatures as high as 8 K. Apart from phosphorescence detection of zero-field resonances, resonances could also be found by observing the delayed fluorescence. These resonances were attributed to the monomer species which has a lifetime on the order of 1 s.
IntroductionThe salts of pseudoisocyanine (PIC) are well-known to form aggregates due to the strong interaction of their n-electrons. Aggregate formation is indicated by the appearance of one or several sharp bands, the so-called J bands, at the red edge of the
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