Fluorescence of Naphthacene Vapor

Williams, R. J. P.; Goldsmith, George J.

doi:10.1063/1.1734574

Cited by 56 publications

(10 citation statements)

References 8 publications

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“…Since only resonance fluorescence is observed from diatomic molecules at low pressures in the gas phase, both internal conversion and intersystem crossing are forbidden processes. Similar low-pressure gas-phase experiments conducted on large polyatomic molecules (naphthalene,3 anthracene,' and naphthacene 6 ) reveal that upon excitation of the second excited singlet state, fluorescence is observed only after internal conversion to highly excited vibrational levels of the first excited singlet state. These two extremes suggest intermediate molecular cases for internal conversion processes where fluorescence from second and higher excited singlet states might have rates competitive with internal conversion to first excited singlet states.…”

Section: Introductionmentioning

confidence: 74%

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Electronic Consequences of Vibrational Deficiency in Polyatomic Molecules

Gardner¹,

Kasha²

1969

The Journal of Chemical Physics

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Vibrationally deficient molecules have been defined as those molecules whose symmetry species for the normal vibrational modes of a molecule fail to span all of the irreducible representations of the corresponding point group. A comprehensive group-theoretical study of all of the finite point groups and of the infinite point groups C∞ν and D∞h has been undertaken in order to determine the extent of vibrational deficiency for various molecular geometries. An important electronic consequence of vibrational deficiency is the identification of special examples of electronic transitions which are forbidden even when considering perturbation by a single antisymmetric normal vibrational mode. Thus, in the second part of this group-theoretical study, electric-dipole selection rules have been determined in order to ascertain possible examples of these forbidden transitions in vibrationally deficient molecules. First-order forbidden vibronic transitions are found to be physically possible in certain polyatomic molecules in D3h, D4h Td, Oh, C∞ν, and D∞h point groups. An analysis of electronic transitions of vibrationally deficient molecules in the above point groups was made in order to establish and to predict examples of this specially forbidden transition which will be manifest as an anomalously weak absorption. A second electronic consequence of vibrational deficiency is predicted in small polyatomic molecules where missing antisymmetric vibrations may have a critical influence on the pathway of intramolecular radiationless processes. The probability of a radiationless transition in an isolated polyatomic molecule may be considered to depend upon a vibrational factor and an electronic factor. This present work indicates that in vibrationally deficient molecules, the electronic factor may have a significant influence on the nonradiative transitions. The fluorescence of SO2 from the second excited singlet state to the ground state is considered as a possible example of the influence of the electronic factor on radiationless processes in vibrationally deficient molecules.

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Section: Introductionmentioning

confidence: 74%

“…From the final results on radiationless transitions, selection rules can be determined very easily using Eq. (6). The one feature that stands out is the effect of spatial degeneracy of the electronic states involved in the radiationless transition.…”

Section: Bl+-i-+bsmentioning

confidence: 99%

Electronic Consequences of Vibrational Deficiency in Polyatomic Molecules

Gardner¹,

Kasha²

1969

The Journal of Chemical Physics

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“…(1) Isolated molecule (low-pressure gas phase) experiments on large (11) and small (12) molecules emphasized and enhanced the intramolecular aspects of radiationless processes. It was shown that large molecules (e.g., naphthalene) can have a sufficiently large number of vibrational degrees of freedom that the molecule can act as its own energy sink, so that electronic relaxation is irreversible in the time range for which the molecule is isolated (up to 10-5 sec).…”

Section: Intramolecular Radiationless Transitionsmentioning

confidence: 99%

“…Physical processes associated with this model are usually such that the system is prepared at t = 0 in state 0a. The state for t > 0 is then given by 'Ht) = E e~iE,tlhcsa}ps (11) The probability amplitude of 4>a is then given by <0a|'Hf)> = Ee-i£-f/'1M2 (12) It turns out that, for t < 2irhA~l, eqn. ( 12) is identically an exponential function (28).…”

Section: Elementary Theoretical Descriptionmentioning

confidence: 99%

Molecular excited state relaxation processes

Rhodes¹

1979

J. Chem. Educ.

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Molecular Excited State Relaxation ProcessesMost molecular processes undergo a monotonle relaxation toward equilibrium. For example, almost all known chemical reactions proceed toward chemical (thermodynamic) equilibrium in a uniform, asymptotic manner. The same is true of a system subjected to a small but sudden temperature jump or of a system of molecules in condensed phase subjected to a short pulse of light from a conventional light source. All of

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“…In these experiments the benzene is not subject to any dissociative process. Williams and Goldsmith (187) studied naphthacene vapor at very low pressure, exciting with either 2537or 3650-Á. Hg lines.…”

Section: Resonance and Nonresonant Radiationmentioning

confidence: 99%