1985 Fiscal Year Final Research Report Summary
A Study on Electronic Relaxation Processes in Molecules by Means of Detection of Extremely. Weak Emission
| Project/Area Number |
59430003
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
構造化学
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| Research Institution | Hokkaido University |
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Principal Investigator |
BABA Hiroaki 北海道大学, 応電研, 教授 (90001669)
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| Project Period (FY) |
1984 – 1985
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| Keywords | Detection of Emission / Electronic Relaxation / Electronically / Excited States / Fluorescence / Phosphorescence |
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| Research Abstract |
A. On the basis of a technique of controlling the voltage impressed on a photomultiplier, a method has been developed which enables one to obtain time-resolved emission free from various types of light noises. B. By the use of the above-mentioned method, an emission spectrophotometric system of extra-high sensitivity has been constructed which employs a pulsed dye laser pumped by an excimer laser as the exciting light source. C. Using this spectrophotometric system, the phosphorescence characteristics of vapors of pyridine and its methyl derivatives were measured quantitatively; the phosphorescence quantum yields are as low as <10^(-7)> <10^(-6)> . D. The triplet ( <pi> , <pi^*> ) and ( <pi> , <sigma^*> ) states that are considered to be responsible for the dual phosphorescence from halogenated benzenes were found to be essentially different from each other in photochemical reactivity. A large-scale ab initio molecular orbital calculation was made of low-lying triplet states of chlorobenzene, with the result that the C-C1 equilibrium bond distance in <^3(pi,sigma^*)> is unusually long. E. For pyrimidine and pyrazine in the vapor phase, the deactivation processes within low-lying triplet states were examined experimentally and analyzed kinetically. The results indicate that the deactivation can be reasonably explained in terms of the stepladder model. F. It was observed for the first time that fluorescence of azabenzenes in the vapor phase is distinctly polarized. G. A quantitative measurement of weak emission from acetaldehyde vapor revealed that the emission characteristics undergo sudden changes at the excitation wavelength corresponding to the threshold energy of photodissociation. H. The fluorescence excitation spectrum was measured for a supersonic molecular beam of phenanthrene. From the width of the absorption band thus obtained, the rate constant of the <S_2> -> <S_1> internal conversion was determined to be about 2 x <10^(12)> <s^(-1)> .
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