The external heavy atom effect: Photophysics of (dimethylamino)benzonitrile in cryogenic rare gas matrices

Journal Article · Thu Apr 20 04:00:00 EDT 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100345a037· OSTI ID:5038708

Morgan, M A; Pimentel, G C ^[1]

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1. Lawrence Berkeley Lab., CA (USA)

The authors have investigated the effects of rare gas external heavy atoms on rate constants of spin-forbidden processes of (dimethylamino)benzonitrile isolated in cryogenic matrices by means of steady-state and time-resolved emission spectroscopy. We interpret the dramatic increase in the phosphorescence yield and the decreases in the fluorescence yield and lifetime and the phosphorescence lifetime in the heavy atom matrices of krypton and xenon in terms of a model in which the rate constant for phosphorescence increases 300-fold in xenon compared to argon, while the rate constants for intersystem crossing to the triplet state and nonradiative relaxation from the triplet state increase by factors of less than 5. Measurements in argon matrices doped with heavy atoms indicate that even one heavy atom neighbor has a significant effect on both single and triplet lifetime. We include higher resolution (up to 0.1 nm) emission spectra of (dimethylamino)benzonitrile detailing vibrational structure which has not previously been observed in the condensed phase. Comparison of the vibrational spacings with a matrix FTIR spectrum indicates that there is distortion of the aromatic ring in the S{sub 1} state, while the shifts in the 0-0 transitions in acetonitrile matrix indicate that the S{sub 1} state is somewhat more polar than either the S{sub 0} or T{sub 1} states.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5038708
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 93:8; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
ARGON
CHEMISTRY
DATA
DE-EXCITATION
ELEMENTS
EMISSION SPECTROSCOPY
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
EXPERIMENTAL DATA
FLUIDS
FOURIER TRANSFORM SPECTROMETERS
GASES
INFORMATION
INFRARED SPECTRA
KRYPTON
LIFETIME
LUMINESCENCE
MATRIX ISOLATION
MEASURING INSTRUMENTS
NITRILES
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHORESCENCE
PHOTOCHEMISTRY
RADIATIONLESS DECAY
RARE GASES
RELAXATION
SPECTRA
SPECTROMETERS
SPECTROSCOPY
VIBRATIONAL STATES
XENON