The two-photon fluorescence excitation spectrum of 1,3-difluorobenzene |
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Authors: | JMichael Hollas Hamdan Musa Trevor Ridley |
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Institution: | Chemistry Department, University of Reading, Reading RG6 2AD, Berkshire, England |
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Abstract: | The system of 1,3-difluorobenzene has been observed using the technique of two-photon fluorescence excitation obtained with a pulsed dye laser. Calibration was achieved by a combination of the neon optogalvanic spectrum and etalon fringes. In circular, compared to linear, polarization the bands divide into two groups, those which are B2-A1 and which retain their intensity with circular polarization, and those which are A1-A1 and lose about 60% of their intensity under the same conditions. These two kinds of bands also show characteristic rotational contours. All of the A1-A1 bands whose assignments are established obtain their intensity through vibronic interaction in which the vibration ν′25 (ν′14 in the Wilson numbering) mixes the with, presumably, the state. There is an important Fermi resonance between the 91 and 101111 levels. Parts of the one-photon absorption spectrum have been photographed to identify sequences associated with the 000 band for comparison with those observed in the two-photon spectrum, and to search for bands involving odd quanta of b2 vibrations, including ν′25 (ν′14); none was found. |
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