Microchannel-plate photomultiplier applicability to the time-correlated photon-counting method

Yamazaki, Iwao; Tamai, Naoto; Kume, Hidehiro; Takahashi, Hiroshi; Oba, K.

doi:10.1063/1.1138027

Cited by 188 publications

(38 citation statements)

References 14 publications

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“…Fluorescence lifetimes were measured on 10 À7 m solutions with a picosecond time-correlated single-photon counting system. [31] Time-resolved transient absorption spectra were measured by using two laser systems. One was for the measurements in picosecond time region and the other was in subpicosecond time region.…”

Section: Methodsmentioning

confidence: 99%

Energy-Gap Dependence of Photoinduced Charge Separation and Subsequent Charge Recombination in 1,4-Phenylene-Bridged Zinc-Free-Base Hybrid Porphyrins

et al. 2000

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A series of 1,4-phenylene-bridged ZP-HP hybrid porphyrins (ZP = zinc porphyrin, HP = free-base porphyrin) 1-8 ZH have been prepared in which an electron-donating ZP moiety is kept constant and electron-accepting HP moieties are varied by introducing electron-accepting substituents, so that the energy gap for charge separation, ZP-1HP*--> ZP(+)-HP-, covers a range of about 0.9 eV in DMF. Here selective excitation at the HP moiety was employed to avoid complication in the determination of electron transfer rates derived from energy transfer, 1ZP*-HP --> ZP-1HP*. Definitive evidence for the electron transfer has been obtained in three solvents (benzene, THF, and DMF) through picosecond-femtosecond transient absorption studies, which have allowed the determination of the rates of the photoinduced charge separation, ZP-1HP* --> ZP(+)-HP-, and subsequent thermal charge recombination ZP(+)-HP- --> ZP-HP. Dyad 1ZH in THF exhibits a biphasic fluorescence decay that indicates thermal repopulation of the ZP-1HP* from ZP(+)-HP-; this has been also supported by the transient absorption spectra. On this ground, the energy levels of the ZP(+)-HP- ion pairs have been estimated. Similar biphasic fluorescence decay has been observed for 5 ZH in benzene; this allows furhter estimation of the energy level of the ZP(+)-HP- ion pairs. The free-energy-gap dependence (energy-gap law) has been probed from the normal to the upper limit region for the rate of the charge separation alone, and only the inverted region for the rate of the charge recombination. It was not possible to reproduce both energy-gap dependencies of the charge separation and the charge recombination assuming common parameter values for the reorganization energy and electronic interaction responsible for the electron transfer with the classical Marcus equation. Although both energy-gap dependencies can be approximately reproduced by means of the simplified semiclassical equation, which takes into consideration the effect of the high-frequency vibrations replaced by one mode of averaged frequency, many features, which include the effects of solvent polarity, electron-tunneling matrix element, and so forth on the energy-gap law, are considerably different from those of the previous studied porphyrin-quinone systems with weaker inter-chromophore electronic interactions.

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Section: Methodsmentioning

confidence: 99%

Energy-Gap Dependence of Photoinduced Charge Separation and Subsequent Charge Recombination in 1,4-Phenylene-Bridged Zinc-Free-Base Hybrid Porphyrins

et al. 2000

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“…Poly(ethylene glycol) and CsI were used as internal standards and 3-nitrobenzyl alcohol as the FAB matrix, and the positive FAB ionization method was used at an accelerating voltage of 10 kV with Xe atoms as the primary ion source. Fluorescence lifetimes were measured in 10 À7 M air-saturated solutions with a picosecond time-correlated singlephoton-counting system [21]. Picosecond transient absorption spectra were measured by means of a microcomputer-controlled double-beam picosecond spectrometer with a picosecond dye laser of 8 ps pulse duration pumped by the second harmonic of a repetitive mode-locked Nd 3 :YAG laser [22].…”

mentioning

confidence: 99%

Orientation Effects on Excited State Dynamics of Zinc Porphyrin–Free Base Porphyrin–Pyromellitimide Triads

Osuka

Shin

Yoneshima

et al. 1999

J. Porphyrins Phthalocyanines

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The synthesis is described of fixed distance triads consisting of zinc porphyrin ( ZP ), metal-free porphyrin ( HP ) and pyromellitimide (I) in which the ZP and HP moieties are bridged by a rigid 4,4'-biphenylene spacer and related spacers, being held with dihedral angles defined by the torsional angle (θ) of the 4,4'-biphenylene spacer varying from nearly coplanar (θ = 0°, phenanthrene spacer) to nearly orthogonal (θ = 90°, 2,2',6,6'-tetramethylbiphenylene spacer). Using these models, the effects of the dihedral angle of the two porphyrins have been examined for singlet–singlet excitation energy transfer from ZP to HP , hole transfer from HP + to ZP and charge recombination of ZP +– HP – I – to the ground state. In the three processes examined, the observed rate constants are roughly in the order of 1d (coplanar)≥1c (nearly coplanar) >1a (tilted) >1b (orthogonal).

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“…We used a timecorrelated single photon counting system (18) for measuring fluorescence spectra and rise as well as decay curves of a small ablated area. The excitation was a frequency-doubled laser pulse (295 nm, lOps) generated from a synchronously pumped cavity-dumped dye laser (Spectra Physics 375B) and a CW mode-locked YAG laser (Spectra Physics 3000).…”

Section: Molecidar Studies On Laser Ablation Processes 403mentioning

confidence: 99%

Molecular Studies on Laser Ablation Processes of Polymeric Materials by Time-Resolved Luminescence Spectroscopy

Masuhara¹,

Itaya

Fukumura

1989

ACS Symposium Series

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By fluorescence analyses just upon laser ablation and of ablated surface, molecular aspects of ablation mechanism were elucidated and a characterization of ablated materials was performed. Laser fluence dependence of poly(N-vinylcarbazole) fluorescence indicates the inportance of mutual interactions between excited singlet states. As the fluence was increased, a plasma-like emission was also observed, and then fluorescence due to diatomic radicals was superimposed. While the polymer fluorescence disappeared mostly during the pulse width, the radicals attained the maxi mum intensity at 100 ns after irradiation. Fluorescence spectra and their rise as well as decay curves of ablated surface and its nearby area were affected to a great extent by ablation. This phenomenon was clarified by probing fluorescence under a microscope.There are a number of reports concerning laser ablation of polymeric materials in relation to microelectronics technology (1-8).Most of the polymers studied were polyimide, poly(methyl methacrylate), poly(ethylene terephthalate) and some photoresists. They have carbonyl as well as amino groups and hetero-atoms. In view of photophysics and photochemistry, this means that fluorescence lifetime is very short, intersystem crossing occurs with high quantum yield, and they are photochemically reactive (9).On the other hand, there are other series of polymers having π-electronic chromophore such as N-carbazolyl and 1-pyrenyl groups, whose photophysical properties are quite different from the above polymers and whose laser chemistry is studied in detail. A relation among interchromophoric interaction, spectral shape and geometrical structure in the excited singlet, triplet, cationic and anionic 1 Current address: ERATO, JRDC (1988-1993), 15 Morimoto-cho, Shimogamo, Sakyo-ku,

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Microchannel-plate photomultiplier applicability to the time-correlated photon-counting method

Cited by 188 publications

References 14 publications

Energy-Gap Dependence of Photoinduced Charge Separation and Subsequent Charge Recombination in 1,4-Phenylene-Bridged Zinc-Free-Base Hybrid Porphyrins

Energy-Gap Dependence of Photoinduced Charge Separation and Subsequent Charge Recombination in 1,4-Phenylene-Bridged Zinc-Free-Base Hybrid Porphyrins

Orientation Effects on Excited State Dynamics of Zinc Porphyrin–Free Base Porphyrin–Pyromellitimide Triads

Molecular Studies on Laser Ablation Processes of Polymeric Materials by Time-Resolved Luminescence Spectroscopy

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