Infrared spectroscopy of proteins.

Photo-, thermo-, solvato-, and electrochromic spiroheterocyclic compounds.

Photophysics of photosynthesis. Structure and spectroscopy of reaction centers of purple bacteria

Ultrafast photochemical reactions in liquids occur on similar or shorter time scales compared to the equilibration of the optically populated excited state. This equilibration involves the relaxation of intramolecular and/or solvent modes. As a consequence, the reaction dynamics are no longer exponential, cannot be quantified by rate constants, and may depend on the excitation wavelength contrary to slower photochemical processes occurring from equilibrated excited states. Such ultrafast photoinduced reactions do no longer obey the Kasha–Vavilov rule. Nonequilibrium effects are also observed in diffusion-controlled intermolecular processes directly after photoexcitation, and their proper description gives access to the intrinsic reaction dynamics that are normally hidden by diffusion. Here we discuss these topics in relation to ultrafast organic photochemical reactions in homogeneous liquids. Discussed reactions include intra- and intermolecular electron- and proton-transfer processes, as well as photochr...

Ultrafast Elementary Photochemical Processes of Organic Molecules in Liquid Solution

X-ray Analysis of Structural Changes in Photochromic Salicylideneaniline Crystals. Solid-State Reaction Induced by Two-Photon Excitation

A nanosecond time-resolved infrared spectroscopic system based on a dispersive scanning spectrometer has been constructed. This is an advanced version of a similar system reported in a previous paper; the time resolution has been improved from 1 μs to 50 ns and the sensitivity from 10-4 in intensity changes to 10-6. These have been achieved by the use of a high-temperature ceramic infrared light source, a photovoltaic MCT detector, and a low-noise, wide-band preamplifier developed specifically for the present purpose. Time-resolved infrared spectra of a few samples of photochemical and photobiological interests are presented to show the capability of the system. The origin of the thermal artifacts, which have been found to hamper the time-resolved infrared measurements seriously, is shown to be due to the transient reflectance change induced by a small temperature jump. The future prospect of time-resolved infrared spectroscopy is discussed with reference to other methods including infrared laser spectroscopy and Fourier transform infrared spectroscopy.

Nanosecond Time-Resolved Infrared Spectroscopy with a Dispersive Scanning Spectrometer

Submicrosecond time-resolved infrared study on the structure of the photoinduced transient species of salicylideneaniline in acetonitrile

Pulsed electric-field-induced reorientation of a ferroelectric liquid crystal (FLC), 5-(2-fluorooctyloxy)-2-(4-hexylphenyl)-pyrimidine, has been investigated by using a dispersive submicrosecond time-resolved infrared spectroscopic technique. The observed absorbance decay for a band at 1440 cm-1 due to a ring-stretching mode of the phenylpyrimidine group indicates that the FLC molecule reorients from a stationary state with a slight delay (less than 1 μs) just after the upswing of the electric field, while counter-reorientation occurs with a delay time of a microsecond after the reverse of the electric field. The delay time for the counter-reorientation changes with temperature, indicating that the viscosity has a strong influence on the delay time. It is also indicated in the present study that the whole FLC molecule reorients simultaneously as a rigid rod in both the preliminary and the counter-reorientation process.

Submicrosecond Preliminary Process of Electric-Field-Induced Reorientation of a Ferroelectric Liquid Crystal, 5-(2-Fluoroalkoxy)-2-(4-n-Alkylphenyl)-Pyrimidine, Studied by Time-Resolved Infrared Spectroscopy:

Investigation of the photoisomerization of all-trans-retinal by singular-value-decomposition analysis of nanosecond time-resolved infrared spectra

Time-resolved resonance Raman and molecular orbital studies of the structures of the transient species involved in the photochromic reaction of 2,2′-spirobi[2H-1-benzopyran]

Tetsuro Yuzawa

Papers

Nanosecond Time-Resolved Infrared Spectroscopy with a Dispersive Scanning Spectrometer

Submicrosecond time-resolved infrared study on the structure of the photoinduced transient species of salicylideneaniline in acetonitrile

Submicrosecond Preliminary Process of Electric-Field-Induced Reorientation of a Ferroelectric Liquid Crystal, 5-(2-Fluoroalkoxy)-2-(4-n-Alkylphenyl)-Pyrimidine, Studied by Time-Resolved Infrared Spectroscopy:

Investigation of the photoisomerization of all-trans-retinal by singular-value-decomposition analysis of nanosecond time-resolved infrared spectra

Time-resolved resonance Raman and molecular orbital studies of the structures of the transient species involved in the photochromic reaction of 2,2′-spirobi[2H-1-benzopyran]