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1

Triplet States and Triplet Excitons in Chemically Mixed Crystals of Acridine with Anthracene

100%

Morawski O., Prochorow J.

Acta Physica Polonica A

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1995

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vol. 88

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issue 3

469-481

EN

Spectral and temporal characteristics and their temperature dependence for the long-lived (phosphorescence and delayed fluorescence) emission of chemically mixed crystals of acridine II (host) with anthracene (guest) were studied under conditions of various spectral resolutions and different modes of excitation. The energy of 0-0 transitions of exciton band and of trap states have been determined and the nature and energy scheme of the triplet states of crystals have been established. The complex arrangement of host molecules into two different pairs in the crystal structure of acridine II is revealed in the energetic "doublet" structure of the trap states for both, the shallow and the deep traps (of acridine and of anthracene origin, respectively). Migration of triplet excitation energy in these chemically mixed crystals is controlled predominantly by the triplet-triplet annihilation of excitons (either heterogeneous or homogeneous) almost in the whole temperature range. The formation of triplet excimers of acridine was definitely ruled out.

2

Cavity Ring Down Measurement of the (1, 0) B ^{2}Σ_{u}^{+} - X ^{2}Σ_{g}^{+} Absorption Band of the N_{2}^{+} Cation

81%

Fulara J., Łapiński L., Morawski O., Prochorow J.

Acta Physica Polonica A

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1998

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vol. 93

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issue 5-6

723-730

EN

The ultraviolet (1, 0) B ^{2}Σ_{u}^{+} - X ^{2}Σ_{g}^{+} transition in the N_{2}^{+} cation was measured with the absorption cavity ring down technique. The N_{2}^{+} cations were produced in a stationary DC discharge in nitrogen under reduced ( ≈ 0.5 Tr) pressure. The weak band due to the (4, 0) A ^{2}Π_{u} - X ^{2}Σ_{g}^{+} transition in the red part of the spectrum was also recorded. Several of the observed transitions correspond to absorptions from the vibrationally excited (ν'=1) states of N_{2}^{+} and to absorptions from the neutral N_{2} molecules in the triplet state.

3

Emission of Acridine and its Aggregates Isolated in the Neon Matrix

81%

Prochorow J., Kozankiewicz B., Dongo Gemi B. B., Morawski O.

Acta Physica Polonica A

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1998

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vol. 94

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issue 5-6

749-760

EN

The results of experimental studies of fluorescence and phosphorescence of acridine in the low-temperature inert neon matrix, at 7 K, are reported. It is found that the low-temperature inert matrix of neon affects the energy levels of acridine molecules very weakly even as compared with nonpolar (aprotic) and non-reactive solvent (e.g. hexane) and that there are different sites for acridine molecules in the neon matrix. However, the observed fluorescence spectra are strongly dependent on the excitation wavelength and besides the different (monomer) sites other emitting species are also contributing to the observed fluorescence emission of acridine in the neon matrix. Clear-cut evidence of the formation of singlet excimers of acridine in the neon matrix demonstrates itself as a very broad and structureless fluorescence spectrum with a relatively large shift from the origin of monomer (site) fluorescence which is characterized by a very distinct vibrational structure. The phosphorescence emission was observed only for the monomers. The observed differences in the low-energy part of excitation spectra of phosphorescence and fluorescence are discussed in terms of the close-lying excited singlet states of n,π* and π,π* character (mixed by the vibronic coupling) and tentatively interpreted as due to the formation of resonance acridine dimers. Their fluorescence spectrum is slightly shifted toward lower energies from the origin of monomer (site) fluorescence.

4

Purely Electronic and Vibronic Fluorescence Excitation of Single Terrylene Molecules in a Naphthalene Crystal

71%

Banasiewicz M., Dresner J., Morawski O., Wiącek D., Kozankiewicz B.

Acta Physica Polonica A

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2007

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vol. 112

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issue S

S-85-S-94

EN

Fluorescence excitation spectra of spatially resolved single terrylene molecules in a naphthalene crystal were studied at 5 K as a function of exciting laser light intensity. The fully saturated fluorescence detection rate for purely electronic transition (0,0) was found to be about twice smaller than that for the two main vibronic components located 239 and 251 cm^{-1} above. This relation is fulfilled when the triplet population rate k_{23} is much weaker than the depopulation rate k_{31}. We propose that the weak fluorescence excitation lines observed at the frequencies of 38, 67, 97, and 145 cm^{-1} correspond to nontotally symmetric low-frequency vibration modes of terrylene.

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Triplet States and Triplet Excitons in Chemically Mixed Crystals of Acridine with Anthracene

Cavity Ring Down Measurement of the (1, 0) B ^{2}Σ_{u}^{+} - X ^{2}Σ_{g}^{+} Absorption Band of the N_{2}^{+} Cation

Emission of Acridine and its Aggregates Isolated in the Neon Matrix

Purely Electronic and Vibronic Fluorescence Excitation of Single Terrylene Molecules in a Naphthalene Crystal