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Articles you may be interested inFlexible microwave absorbers based on barium hexaferrite, carbon black, and nitrile rubber for 2-12GHz applications Absolute vibrational and electronic cross sections for low-energy electron (2-12 eV) scattering from condensed pyrimidine J. Chem. Phys. 122, 094701 (2005); 10.1063/1.1854121 μm InGaAs-InGaAlAs-InP diode lasers grown in solid-source molecular-beam epitaxyWe have obtained well resolved optical spectra of a simple, methyl substituted hexaene at 4.2 K. These spectra provide detailed information on the vibronic levels associated with the ground (I lAg) and first excited (2 lAg) singlet electronic states. The strongest vibronic feature, due to a totally symmetric CC double bond stretch, shifts from 1576 cm-I in the l1A. state to 1779 cm-I in the 2 IA. state. This shift, not accounted for by current theoretical descriptions of polyene electronic states at the crude adiabatic level, may be rationalized as a manifestation of vibronic coupling between the ground and first excited singlet states.4

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Lifetimes of separate conformational states of two tryptophan derivatives, 3-indolepropionic acid and TV-acetyltryptophan ethyl ester (NATE), excited at their S, origins have been measured in supersonic expansions. The lifetimes for the A and B conformations are respectively 16.2 ± 0.1 and 13.5 ± 0.1 ns for 3-indolepropionic acid and 13.5 ± 0.1 and 10.9 ± 0.3 ns for NATE. These values differ for separate conformers and are notably different from lifetimes for the same molecules in solution. While different emitting conformers may explain the multiexponential emission in solution, solvent interactions must also play a very significant role.

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Experiments on the laser excited fluorescence spectrum of perylene in n-octane and ethanol hosts at low temperatures are reported. Monochromatic excitation leads to a dramatic sharpening of the emission lines. The dependence of the spectrum on both excitation wavelength and temperature are presented and discussed qualitatively in terms of a model which applies the basic concepts of the theory of mixed crystal spectra to systems with inhomogeneous broadening.