[en] The adsorption and desorption dynamics of organic cations, Malachite Green (MG), on the anionic lipid monolayer at an air/water interface were investigated in real time by using the optical second harmonic generation (SHG) technique. We showed the average orientation of the adsorbed MG on the lipid monolayer to be almost constant during the adsorption process, which is necessary to get the MG adsorption dynamics from the observed SH field change. When we increased the subphase salt concentration after saturation of the MG adsorption, the SHG field exponentially dropped with time due to MG desorption. Both the adsorption and the desorption rates show linear proportions to the subphase MG concentration, which agrees with the theoretical consideration. This application of SHG for the real-time observation of the adsorption and desorption dynamics on a lipid monolayer can be complementarily used with the steady-state SHG measurement to study many relevant biological problems.

[en] The electro chemical sensors are thought to be an ideal tool for trace gas analysis, but they have many problems to be solved until now. It is two decades since CRDS was introduced and the principles and important methods are understood and developed very well, now. However, CRDS is a vivid research area at this time, too. The main issue is the development of compact and cheap spectrometers having ultra sensitive analysing capability. For this purpose, many variations of CRDS, such as cw CRDS (or CALOS: cavity leak out spectroscopy), cavity enhanced optical heterodyne spectroscopy, cavity enhanced frequency comb spectroscopy, etc. have been introduced. We developed a cw CRDS spectrometer in near IR region for the application to medical diagnosis by analysing trace molecules in the human breath gas. The needed sensitivity is sub ppb (parts per billion) level. In general, the absorptions of VOC (volatile organic compound) molecules in this near IR region, which are overtone vibrational bands, are weaker than those of the fundamental vibrational lines in mid IR region, so that ultra sensitive spectrometers can be realized much easily, which overcome the weakness of the molecular absorption lines. We used an external cavity diode laser (New Focus, model velocity 6300) and a low noise and high gain photo receiver (New Focus model 2053 FS). A pair of mirrors with 99.998% of reflectivity (2m radius of curvature, ATFilms, inc.) were used for the cavity of 1m length. To realize fast ring down events with high signal to noise ratio signals, we developed an auto tracking system by use of an digital to analog converter (NI PCI 6733). Under auto tracking, the average sweeping range of the cavity resonance is around several MHz and the acquisition speed of the cm"-1"/Hz"1/2", and the corresponding analysing sensitivities in real time for methane and ethane are 20 ppt (parts per trillion) and 200 ppt, respectively

[en] Spatial distortions, such as self-focusing, self-defocusing and conical emission, of the pulsed laser beam interacting with near-resonant samarium atoms are modified using electromagnetically induced transparency. Depending on the power and the detuning of the coupling and the probe lasers, beam shape is retrieved.

[en] We determined the electric quadrupole and magnetic dipole interaction constants and isotope shifts of Sm I lines between 550 nm and 560 nm. Atomic samarium having electrons in d and f shells with a large number of transition lines in the visual region imposes great challenges in spectroscopic analysis. The large isotope shifts of Sm I make the study of isotope shifts of samarium particularly interesting. Samarium atomic vapor was generated in a high temperature oven (900 .deg. C) and then ejected through an 1 mm orifice from the oven into an open region in a vacuum chamber. The atomic beam was excited by a probe laser, which was ring dye laser (Coherent 699-21) with a linewidth less than 1 MHz. The direction of the laser was perpendicular to the atomic beam so as to eliminate the doppler shift. Since the atomic beam had a small divergence, only the central part of the beam illuminated by the probe laser was imaged to a photon-counting detector (photomultiplier tube). The resulting spectral resolution was less than 30 MHz, which was mostly due to power broadening and residual doppler shift. We surveyed the hyperfine structures and isotope shifts of more than 10 fine structure lines between 550 nm and 560 nm.

[en] We report the first observation of hyperfine structures (HFSs) and isotope shifts (ISs) of Sm I in the range of 540-560 nm using an atomic beam resonance-fluorescence technique. The least square fitting was used to determine hyperfine constants in 4f⁵5d6s² and 4f⁶6s6p of atomic samarium (Sm I). The isotope shifts of 18 transition lines were also determined and analyzed by the King plot

[en] We have observed dynamic effects of a pre-ablation spark on the signal intensity in the orthogonal dual-pulse laser-induced breakdown spectroscopy. We applied pre-ablation and ablation laser pulses with significantly reduced energy for an aluminum metal in open air. Under this experimental condition, the well-known signal enhancement through the increase in ablated mass was negligible. The Al I and II emissions were investigated by both top-view and spatially-resolved side-view collection modes. In this low laser power regime, dynamic effects of a pre-ablation spark on the signal intensity were clearly revealed. The principal factor of signal enhancement is the increase in temperature. Without the mass removal enhancement, effective rarefaction leads to decrease in the Al I emission intensity and simultaneous increase in the Al II emission intensity. This is attributed to the role of Saha equilibrium. Selective prolongation of emission lifetime only for the enclosed part of the analyte plasma in the rarefied region and other fluid-dynamic effects of a pre-ablation spark have been visualized by wavelength-selected time-space correlation maps of plasma emissions.