A CW CO2 laser oscillates at the wavelength range of 9-11μm, where various molecules have the fundamental vibrational band. In our laboratory, a widely tunable CO2 laser sideband system has been developed for high-resolution spectroscopy and applied to a microwave (MW)-infrared (IR) double resonance spectrometer and a Starkmodulated sub-Doppler resolution spectrometer. The present article reports operation principles, features, and practical techniques of the CO2 laser sideband system and application to high-resolution spectroscopy of methanol. The results show high performance of the CO2 laser sideband system for studying molecular spectroscopy.
A protein in solution is a thermodynamic entity existing in equilibria among multiple conformations from the folded to the unfolded. Various experimental results indicate that transitions to higher energy conformers are crucial for function in many proteins. However, our knowledge on higher energy conformers is extremely limited at present, compared to the knowledge about the folded counterparts. A newly emerging technique, the variable pressure NMR method, enables us to explore a much wider conformational space of proteins than hitherto explored by X-ray crystallography and conventional NMR technique, giving a new dynamic view of proteins that amply fluctuate over the entire conformational space.
A growth of nanoscience requires spectroscopy which allows us to measure a nanometer scale with a high accuracy. Time-domain ESR spectroscopy has been recently developed to detect small exchange and dipolar interactions that are effective even between two spins with subnano or nano meter separations. This review focuses the advanced time-domain ESR spectroscopic studies on nanoscale structure and dynamics in amorphous or glassy samples.
We have constructed a fluorescence lifetime imaging (FLIM) system to study the photo-induced dynamics of living cells. The output from a femtosecond mode-locked Ti: sapphire laser is frequency-doubled and focused onto the sample with an objective lens of a confocal microscope. The fluorescence decay of the sample is measured at each pixel of a scanning image. Each fluorescence lifetime is evaluated quickly using time-gating electronics, and the fluorescence lifetime image can be obtained within several minutes. We have combined the FLIM system with a picosecond time-correlated single-photon counting system in which a microchannel-plate photomultiplier is used for detection, so that the value of the fluorescence lifetime at a position can be analyzed quantitatively. A high contrast light-scattering image of a polymer film is also found to be obtained with the FLIM system.
Nuclear Magnetic Resonance (NMR) is one of the key methodology of spectroscopy, which is based on the resonation between nuclear spin and radio frequency electric wave under the strong magnetic field. Although NMR began its history as a phenomena of quantum physics, its modern pulse-FT NMR have been widely applied in the area of analytical chemistry, molecular biology, medicine and quantum computing. In this review, the basic theory of NMR is introduced according to the classical magnetization model rather than the view of quantum mechanics. The meaning of the data available from NMR, such as chemical shift, spin coupling, and coupling constant as well as basics of density matrix and product operator formalism is briefly described.