Mechanisms of the delayed luminescence of N-methylindole and indole in the gas phase

Borisevich, N. A.; Sukhodola, A. A.; Tolstorozhev, G. B.

doi:10.1016/j.chemphys.2008.09.002

Cited by 8 publications

(11 citation statements)

References 15 publications

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“…Decreasing the wavelength of the exciting radiation at the same pressure of foreign gas led to an increase in all instances of the contribution of the fast component to the build-up kinetics. It is also noteworthy that instantaneous spectra of delayed luminescence of indole gas are independent of the recording time on the build-up curve and agree with the spectrum of this emission [5]. Figure 3 shows the kinetics of delayed luminescence build-up of indole in the gas phase as a function of the intensity of the exciting radiation.…”

supporting

confidence: 66%

“…Delayed luminescence with a maximum at 535 nm due to free radicals formed from dissociation of an N-H bond was observed during a study of indole in high-temperature gases [5]. A growth of its intensity (build-up) related to the formation of free radicals was observed in the initial portion of the kinetics of this emission at times up to 10 μs.…”

Section: Introductionmentioning

confidence: 94%

“…This produces a fast increase in the rate constant for dissociation of an N-H bond. However, later studies [4] showed that the reason for the low fluorescence quantum yield may be fast internal conversion into the ground electronic state that occurs from the πσ * -or directly from the ππ * -state.Delayed luminescence with a maximum at 535 nm due to free radicals formed from dissociation of an N-H bond was observed during a study of indole in high-temperature gases [5]. A growth of its intensity (build-up) related to the formation of free radicals was observed in the initial portion of the kinetics of this emission at times up to 10 μs.…”

mentioning

confidence: 94%

“…The intensity of each component is proportional to the square of the intensity of the exciting radiation. According to the model proposed in the literature [5], delayed luminescence of indole in the gas phase is due to luminescence of free radicals that are formed by dissociation of an N-H bond upon excitation of the molecules in the electronic absorption band. The excited states of the radicals are populated as a result of energy transfer from indole triplet states.…”

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confidence: 99%

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Indole photodissociation in the gas phase

Sukhodola

2011

J Appl Spectrosc

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A. A. SukhodolaUDC 535.372:547.751 Kinetic characteristics of the growth in delayed luminescence intensity of indole in the gas phase have been measured with excitation of the molecules in the spectral region 250-287 nm. The luminescence build-up kinetics show two components with characteristic lifetimes of about 1 and 10 μs that are associated with the formation of free radicals due to N-H bond dissociation. Two basic mechanisms for photodissociation of indole in the gas phase have been identified based on an analysis of the dependence of the kinetic characteristics for these components on the excitation radiation wavelength/intensity and the vapor pressures of indole and foreign gases. The fast component results from the dissociation of an N-H bond of vibrationally excited molecules in the ground state that is populated through internal conversion. The slow component is associated with the generation of free radicals because of annihilation of two triplet indole molecules. A dependence of the quantum yield of intersystem crossing on the excitation wavelength in the spectral region 260-287 nm has been found. It is shown that the fluorescence quantum yield drop with a decrease of the excitation radiation wavelength is caused by an increase in the internal conversion quantum yield to the electronic ground state. Keywords: indole, free radical, triplet state, kinetics of delayed luminescence. Introduction.A low fluorescence quantum yield and a fast increase of the rate constant for non-radiative transitions with increasing energy of the exciting quantum are typical properties of biologically important indole and its derivatives [1]. This is related to the existence of one or several channels for fast non-radiative relaxation of its lowest excited singlet ππ * -state. It was assumed initially that dissociation of an N-H bond was such a channel. Its rate constant increases with decreasing wavelength of the exciting radiation. Quantum-chemical calculations [2, 3] suggested that the dissociation processes occur owing to coupling of the excited ππ * -state with a near-lying dissociative πσ * -state, the energy of which is slightly greater than that of the ππ * -state. The efficiency of populating the πσ * -state increases with increasing energy of the exciting quantum. This produces a fast increase in the rate constant for dissociation of an N-H bond. However, later studies [4] showed that the reason for the low fluorescence quantum yield may be fast internal conversion into the ground electronic state that occurs from the πσ * -or directly from the ππ * -state.Delayed luminescence with a maximum at 535 nm due to free radicals formed from dissociation of an N-H bond was observed during a study of indole in high-temperature gases [5]. A growth of its intensity (build-up) related to the formation of free radicals was observed in the initial portion of the kinetics of this emission at times up to 10 μs. A study of the luminescence kinetics in this time range enabled the formation mechanism of the free radicals to be analyz...

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confidence: 66%

Section: Introductionmentioning

confidence: 94%

mentioning

confidence: 94%

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confidence: 99%

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Indole photodissociation in the gas phase

Sukhodola

2011

J Appl Spectrosc

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“…The triplet state lifetime of the studied indoles determined from flash photolysis studies Due to the higher concentration of the studied indoles required in flash photolysis, the equation for decay of triplet states T(t) should take into account both the decay due to monomolecular (first-order) processes (from a combination of unimolecular decay and pseudo-first-order processes such as quenching by impurities) and due to second-order triplet-triplet annihilation processes [28,29]:…”

Section: Heavy Atom Effectmentioning

confidence: 99%