Masahide Terazima

Measurement of the triplet lifetime and the quantum yield of triplet formation of phthalazine by the time-resolved thermal lens method

Abstract The time-resolved thermal lens technique is used to determine the quantum yield of the triplet formation and the triplet lifetime of phthalazine in a polar and a non-polar solvent. The quantum yields of phthalazine in ethanol and benzene are 0.44 and 0.49, respectively. Very short triplet lifetimes of phthalazine (2.7 μ;s) in benzene at room temperature are reported.

The quantum yield of triplet formation and triplet lifetime in the solid phase by a time-resolved thermal lens method. Application to pyridazine

Abstract The time-resolved thermal lens technique is used to measure quantum yields of triplet formation and triplet lifetime in the solid phase at low temperature. The time dependence of the thermal lens signal of pyridazine in the solid phase is very different from that in a fluid medium. These results are discussed.

CIDEP studies on the intramolecular hydrogen abstraction reaction of polymethylene linked system. Population relaxation between the ST0 mixed states

Abstract An anomalous intensity pattern in the biradical CIDEP spectrum is observed in an intramolecular hydrogen abstraction reaction system. The intensity pattern is successfully interpreted by the biradical CIDEP theory proposed by Buckley et al. (1987) and Closs et al. (1987), assuming fast population relaxation between the central two Sue5f8T0 mixed states.

The quantum yield of triplet formation and triplet lifetime of pyridine in the liquid phase by the two-photon-excited time-resolved thermal lens method

Abstract The quantum yield of triplet formation and the triplet lifetime of pyridine are measured for the first time in the liquid phase using the two-photon-excited time-resolved thermal lens method. The triplet lifetime (1.0 μs) is very short and the quantum yield of the triplet formation (0.9) is large. These results are discussed in comparison with the same parameters reported for the gas phase.

Is singlet oxygen formation dominant in triplet quenching processes ? Measurement of the quantum yield of singlet oxygen formation by the time-resolved thermal lens method

The quantum yields of singlet oxygen formation (ØΔ) by the quenching of triplet states of organic sensitizers are measured at various concentrations of the sensitizers by using the time‐resolved thermal lens method. Above a certain concentration, ØΔ is independent of the sensitizer concentration. Below the threshold, ØΔ gradually decreases as the concentration of the sensitizer decreases. The extrapolation of ØΔ to zero concentration indicates that singlet oxygen formation is not necessarily dominant in the quenching process even for the 3ππ* state in benzene.

Observation of transient absorption by using the thermal lens method

The application of thermal lens spectroscopy to the absorption measurement of the transient species is demonstrated. The unique advantages of this method are discussed.

Measurement of the quantum yield of triplet formation (φISC) in a polymer matrix by the time-resolved thermal lens method: excitation wavelength dependence of φISC of N-methyl-p-nitroaniline

Abstract The time-resolved thermal lens method is demonstrated to be suitable for measuring the quantum yield of the triplet formation (φISC) of organic molecules in a polymer matrix at room temperature when triplet lifetimes at low temperature are longer than the thermal diffusion time. This method is applied to the measurement of φISC of N-methyl-p-nitroaniline in poly(methyl methacrylate) as a function of the excitation wavelength. The excitation wavelength dependence of the intensity ratio of phosphorescence to fluorescence is discussed on the basis of this result.

Study of the linewidth of the CIDNP-detected ESR spectrum

Abstract Microwave-power dependence of the linewidth of the CIDNP-detected ESR spectrum in the photolysis of ]-benzoquinone has been investigated. The linewidth of the dynamic nuclear polarization spectrum increases with increase of the microwave power, whereas that of the stimulated nuclear polarization spectrum is almost independent of the power. These observations indicate that the linewidth of the dynamic nuclear polarization (DNP) spectrum is governed by the microwave power, and that the broad feature of the stimulated nuclear polarization (SNP) spectrum comes from the short lifetime of the intermediate radical pair.

The exchange interaction in the radical pair in 2-propanol solution as studied by the CIDNP multiplet pattern

Abstract The exchange interaction in the radical pair in homogeneous solution has been investigated by using the CIDNP method. The experimental observations of the multiplet pattern were compared with the theoretical simulations in which the exchange integral was a variable parameter. The results show that 2-propanol is a unique solvent in that the exchange integral in the radical pair in this solvent is large.

Detection of a stimulated emission process as an inverse thermal lens signal

A stimulated emission process is detected by applying the transient thermal lens (TL) technique developed recently. The observed inverse TL signal compared with the conventional TL signal indicates that a convex thermal lens is created in the solution by the stimulated‐emission process. The sensitivity and the advantages of this method are discussed.