Anomalous vibrational relaxation of a hot S*1 state of 3,4-benzpyrene in 2-methylpentane

Two anomalous emission bands in the fluorescence spectrum of 3,4-benzpyrene, dissolved in 2-methylpentane, have been studied as a function of temperature. These emissions originate from the second excited singlet state S₂, and from a vibrationally excited S₁ (S^*₁) respectively. From the temperature dependence of the relative yield and the decay time of the S^*₁ emission it can be concluded that the vibrational relaxation of this state is hampered. The rate constant for this relaxation process is smaller that 4 > 62;x 10⁷ sec^?1.     

Dual fluorescence (S1, S2) in chrysene and 3,4-benzophenanthrene

S₂ and S₁ fluorescence of chrysene and 3,4 benzophenanthrene has been observed in the vapour phase under collision free conditions. It is shown that the intermediate strong couplinng model can be applied to these molecules. The efficiency of the transfer of the excess energy to collision partners is given for different gases.     

Incomplete vibrational relaxation of pyrene in its first excited singlet state in the vapour phase

The non-exponential fluorescence decay of pyrene is assigned to incomplete vibrational relaxation in the first excited singlet state. The increasing rate of this fluorescence decay with increasing vibrational energy is mainly attributed to an increase of the intersystem-crossing rate and to a smaller extent to a temperature dependence of the radiative rate constant.     

SCF—CI calculations and the assignment of the absorption spectrum of the excimer of 1-methyl naphthalene; relation to 1,1′-binaphthyl

An SCF MO calculation followed by extensive configuration interaction between all singly-excited singlet states has been performed for the excimer of naphthalene in a perfect and in some distorted sandwich structures. With these results an assignment is given for the bonds in the absorption spectrum of the excimer of 1-methyl naphthalene. It is further shown that the similarity between the optical properties of the 1-methyl naphthalene excimer and those of 1,1′-binaphthyl in fluid solution, is also reflected by the calculations.     

Noble-gas broadening of an optical transition of I2 measured by coherent transients. III. Two-pulse photon echo and free induction decay

We report two-pulse photon echo decay and free induction decay measurements of iodine as a function of noble-gas pressure. The non-exponential behavior of the two-pulse photon echo decay which in contrast to the free induction decay shows a t³ dependence, is extensively discussed. A comparison with the results of the three-pulse stimulated echo measurements is made. The results are interpretated in terms of a quantum mechanical transport equation, and analytical expressions are derived for the three-pulse stimulated echo, two-pulse echo and free induction decay.     

Untersuchung von Fleisch, Fleischextrakt und Wurstwaren

Ohne Zusammenfassung     

The influence of the molecular conformation upon spectroscopic properties of 1,1′-binaphthyl

The large difference in S₁ → S_n absorption spectrum, fluorescence spectrum and fluorescence decay time of 1,1′-binaphthyl in fluid solution as compared to rigid solution can be related to a change of the molecular conformation of the fluorescent state.     

Fluorescence decay of pyrene vapour; biphotonic excitation and the kinetics of vibrational redistribution

A computer simulation procedure has been applied to the fluorescence decay curves of pyrene vapour, excited into the S₁ state with short laser pulses. The results confirm that the kinetic model which has been used previously in order to describe the effect of vibrational redistribution on the fluorescence decay, is consistent with the experimental decay curves. A very short decay component (τ ≈ 4 nsec) which appears when the energy of the laser exceeds 1.5 mJ is ascribed to doubly excited pyrene molecules.