Электронное строение и спектрально-флуоресцентные свойства лазерных красителей тиопирило-4-трикарбоцианинов

It was found that the long-wavelength absorption band of the laser dye IR 1061 and its analogue with an unsubstituted polymethine chain is strongly broadened and decreases in intensity in polar solvents, while the fluorescence band remains narrow and practically does not change in a wide range of solvent polarities. Based on the quantum-chemical calculations of these dyes by the ab initio DFT/B3LYP/6-31G (d,p) and TDDFT methods, taking into account the polarity of the medium by the PCM method, it is shown that the reason for this difference is the weakening of solvation in the fluorescent state as compared to the ground state due to the greater equalization of the charge in the first than in the latter. An increase in the alternation of bond orders in the polymethine chain in the fluorescent state was found, which causes an increase of vibronic interactions in the radiative transition as compared to the absorptive one. Spectral effects caused by a change in the angle of rotation of phenyl groups in the thiopyrylium cycle upon excitation have been analyzed.

Elucidating the role of structural fluctuations, and intermolecular and vibronic interactions in the spectroscopic response of a bacteriophytochrome

Molecular dynamics and a multiscale polarizable QM/MM strategy allow reproducing absorption, circular dichroism, and resonance Raman spectra of a bacteriophytochrome.

Ultrafast Relaxation Dynamics of the S1 (nπ*) State and the 3p and 3d Rydberg States in Cyclohexanone by Femtosecond Photoelectron Imaging

<div>The radiationless decay dynamics of the S1 (nπ*) state and the 3p and 3d Rydberg states of cyclohexanone are investigated using femtosecond time-resolved time-of- flight mass spectrometry and photoelectron imaging spectroscopy. After two-photon excitation of the 3p and 3d states, an ultrafast population transfer to the 3s state is observed within < 120 fs. We ascribe this behavior to strong vibronic interactions of the excited Rydberg states with the ¹ππ* valence state that enable an ultrafast population transfer via an avoided crossing and the subsequent passage of a conical intersection between the respective electronic states. Eventually, the 3s state deactivates by internal conversion to the S₁ (nπ*) state, which in turn is found to be long-lived with a decay time of ~ 300 - 800 ps.</div>

Ultrafast Relaxation Dynamics of the S1 (nπ*) State and the 3p and 3d Rydberg States in Cyclohexanone by Femtosecond Photoelectron Imaging

<div>The radiationless decay dynamics of the S1 (nπ*) state and the 3p and 3d Rydberg states of cyclohexanone are investigated using femtosecond time-resolved time-of- flight mass spectrometry and photoelectron imaging spectroscopy. After two-photon excitation of the 3p and 3d states, an ultrafast population transfer to the 3s state is observed within < 120 fs. We ascribe this behavior to strong vibronic interactions of the excited Rydberg states with the ¹ππ* valence state that enable an ultrafast population transfer via an avoided crossing and the subsequent passage of a conical intersection between the respective electronic states. Eventually, the 3s state deactivates by internal conversion to the S₁ (nπ*) state, which in turn is found to be long-lived with a decay time of ~ 300 - 800 ps.</div>