The dynamics of populating and depopulating the phosphorescent triplet state as studied by microwave induced delayed phosphorescence

Schmidt, Jan; Antheunis, D.A.; Waals, J.H. van der

doi:10.1080/00268977100102311

Cited by 174 publications

(60 citation statements)

References 20 publications

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“…In many cases, the assumptions are not valid. In particular, SLR usually can not be ignored even at 1·3 K for triplet states which have sublevel decay constants the order of one sec [13]. Also, under strong optical pumping of a dilute system with a long triplet lifetime, the steady state populations of the phosphorescent state and the ground singlet state may be comparable or even inverted.…”

Section: Discussion Of the Methodsmentioning

confidence: 99%

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Kinetics of the triplet state of 2,3-dichloroquinoxaline from microwave-induced phosphorescence transients

1973

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The phosphorescent state of 2,3-dichloroquinoxaline doped into single crystals of durene and 1 ,2,4,S-tetrachlorobenzene has been studied using several methods based upon optical detection of magnetic resonance (ODMR). Flash excitation and continuous optical pumping methods are described and analysed. Phosphorescent transient effects caused by spin-lattice relaxation and variable intersystem crossing rates are observed and described using first-order solutions of the appropriate rate equations. The effects of spatial polarization of the phosphorescence (anisotropic spatial distribution of phosphorescence intensity) of single crystals on ODMR signals is observed and discussed. The spatial polarization of emission can cause difficulties in determining relative radiative rate constants of the triplet sublevels in oriented samples, but can yield information about the linear polarization of the emission analogous to that obtained by conventional means using polarizers.

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Section: Discussion Of the Methodsmentioning

confidence: 99%

“…In many cases, however, the data are found to be still influenced by spin-lattice relaxation, even at the lowest temperatures achieved in pumped-helium experiments (1·1-1·2 K) [13].…”

Section: + D Schweitzer Et Almentioning

confidence: 99%

Kinetics of the triplet state of 2,3-dichloroquinoxaline from microwave-induced phosphorescence transients

1973

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“…2 -these pathways are highly spinselective and provide a characteristic "fingerprint" of electronic structure. In consequence, ISC into the lowest triplet state of a symmetric molecule like naphthalene or quinoxaline in general occurs almost exclusively through a single spin component [35,36] (the upper one T x in the case of Fig. 7) and the phosphorescence likewise is preferentially emitted by a single component.…”

Section: The Optical Pumping Cycle -Detection Of Epr Transitions Betwmentioning

confidence: 99%

“…By means of such "microwave-induced delayed phosphorescence" (MIDP) [36,38] and analogous microwave-saturation-recovery [39] experiments, as well as "microwave phosphorescence double resonance" (PMDR) experiments [40] an impressive amount of information has now been collected on the zero-field splitting and kinetics of populating and decay of phosphorescent triplet states. This is illustrated by a review [41] of what has been achieved during the first decade after these techniques had been introduced.…”

Section: The Optical Pumping Cycle -Detection Of Epr Transitions Betwmentioning

confidence: 99%

EPR of photo-excited triplet states: A personal account

Waals

2001

Appl. Magn. Reson.

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A sketch is presented of the path that has led from Zavoisky's pioneering experiments to modern investigations by electron paramagnetic resonance (EPR) of the phosphorescent (S = 1) triplet state of polyatomic molecules or ions. The group-theoretical method first introduced by Wigner in his analysis of the multiplets of atomic spectroscopy, likewise provides a key for understanding the zero-field splitting and selection rules for radiative decay of the phosphorescent triplet state. Examples to illustrate the progress made through EPR experiments are selected from three fields. (i) Conformational instability on excitation. Both the zero-field splitting and the electron spin density distribution provide unique fingerprints of a triplet state's geometry -structural information of a kind that is nonexistent for singlet states! Illustrations are provided by benzene C 6 H6 and fullerene C60 . (ii) The optical pumping cycle. The spin selectivity of singlet-to-triplet intersystem crossing and radiative decay of the individual spin components of the triplet state is discussed. In practice this selectivity is put to advantage by performing EPR on triplet states in zero-field by means of optical detection. In turn, such experiments have led to a detailed insight into the spin-orbit coupling mechanisms responsible for the spin selectivity of the above processes. The high sensitivity attainable with optical detection has recently culminated in EPR experiments on single molecules. (iii) Quantum interference. In a triplet state of low symmetry two of the spin sublevels may decay to the ground state by the emission of photons of a common polarization (i.e., out of plane for an aromatic hydrocarbon). In such a situation quantum interference between the two decay channels can be induced by an appropriate preparation of the excited state. An example is shown where flash-excitation in the singlet manifold followed by rapid intersystem crossing causes the S = 1 spin angular momentum to be created in a spin state which is not an eigenstate of the zero-field splitting tensor. This nonstationary character of the initial triplet state, which reflects the spin-orbit coupling pathway, is observed through the detection of a spontaneous microwave signal following the 25 ps laser flash.

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“…Two observations relevant to the development of TREPR were made around 1970: CIDEP (chemically induced dynamic electron polarization) in photochemical reactions [I, 2] and spin polarization in organic triplets [3,4]. These observations showed non-Boltzmann distributions among spin sublevels after photochemical reactions and creation of triplet states via intersystem crossing from excited singlet states, respectively.…”

Section: Introductionmentioning

confidence: 99%

Developments of magnetic-resonance-related spin chemistry in Japan

et al. 2003

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Abstraet. A review on the developments of the magnetic-resonance-related spin chemistry in Japan is presented. We describe how studies in this atea started in Japan and developed into the flourishing state of the present. Important contributions made by Japanese spin chemists in the last two decades in three areas, namely, work on chemically induced dynamic electron polarization, excited states and controlling of photochemical reactions, are presented. More emphases are placed on the new deveIopments in recent years, particularty new concepts and new methodologies.

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The dynamics of populating and depopulating the phosphorescent triplet state as studied by microwave induced delayed phosphorescence

Cited by 174 publications

References 20 publications

Kinetics of the triplet state of 2,3-dichloroquinoxaline from microwave-induced phosphorescence transients

Kinetics of the triplet state of 2,3-dichloroquinoxaline from microwave-induced phosphorescence transients

EPR of photo-excited triplet states: A personal account

Developments of magnetic-resonance-related spin chemistry in Japan

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