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Tuning, excited-state, with pressure

In contrast to borazine, the three corresponding excited singlet states of benzene have a much wider spread of absorbing wavelengths and exhibit easily distinguished vibrational fine structure. Many photolysis experiments have been performed using laser lines tuned to selective excite a particular vibrational level of a particular excited state of benzene. Such experiments are more difficult with borazine. The triplet states of benzene have been located experimentally and quantum yields for fluorescence and phosphorescence at various wavelengths and pressure conditions have been determined. [Pg.12]

The typical results reported in this chapter, clearly demonstrate how the lifetime of excited states and the low-spin/high-spin character of such states can be tuned by pressure. Furthermore, photochemical bond formation and cleavage processes are accelerated or decelerated by pressure, respectively, in a similar way as found for the corresponding thermal reactions. As a result of this, the associative or dissociative nature of such substitution reactions can be characterized. A further characterization of the intimate nature of the reaction mechanism can also be obtained for photochemical isomerization and electron-transfer reactions as reported in Sections V and VI, respectively. The same applies to photoinduced thermal reactions, where the interpretation of the pressure dependence is not complicated by photophysical relaxation processes. The results for the subsequent thermal reactions can be compared with a wealth of information available for such processes [1-6]. Especially the construction of reaction volume profiles has turned out to be a powerful tool in the elucidation of such reaction mechanisms. [Pg.139]

The obvious experiment is to retreat from high pressures and to attempt the more difficult task of working with low pressures where relaxation can occur from levels initially pumped in absorption. Then if we can use narrow-band excitation tuned to a single absorption band that terminates in a single vibronic level, a vibrational spectrum of excited state relaxation can be constructed. A detailed picture of the role of various... [Pg.407]

Photochemists have long cherished the goal of mapping the course of excited state relaxation as a function of vibrational activity in the excited state. The most obvious experimental path is to use narrow-band excitation tuned to single absorption bands of gases at very low pressures. This technique, however, will be successful only with molecules possessing the following rather restrictive set of properties. [Pg.411]


See other pages where Tuning, excited-state, with pressure is mentioned: [Pg.61]    [Pg.89]    [Pg.193]    [Pg.61]    [Pg.89]    [Pg.193]    [Pg.167]    [Pg.74]    [Pg.87]    [Pg.63]    [Pg.67]    [Pg.70]    [Pg.89]    [Pg.90]    [Pg.910]    [Pg.3]    [Pg.129]    [Pg.930]    [Pg.530]    [Pg.155]    [Pg.383]    [Pg.180]    [Pg.465]    [Pg.93]    [Pg.17]    [Pg.202]    [Pg.362]    [Pg.68]    [Pg.494]   
See also in sourсe #XX -- [ Pg.89 , Pg.90 , Pg.91 ]




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Excited state tuning

Pressure tuning

State pressure

Tuning

With pressure

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