Takahiro Kasuya

Internal Motions of Hydrazine

The internal motions of hydrazine molecule is studied from its microwave spectrum. Features of spectral lines caused by the inversion and internal rotation of amino group are briefly described together with the determination of the barrier heights of the hindering potential functions.

Microwave Spectrum of Ethyl Iodide, II.

The potential barrier which hinders the internal rotation in ethyl iodide molecule was studied. If the potential energy is assumed to be of the sinusoidal form \(\frac{H}{2}(1-\cos\ \text{3x})\), the barrier height is determined as H =3.22±0.5 kcal/mole from the Q b -type transition in the first excited torsional state. The torsional frequency is about 230 cm -1 . The effect of internal rotation on the quadrupole hyperfine structure of K =1 levels was analyzed.

Predissociative lifetimes of single rovibronic levels of the B 3Π0+(v′=3) state of ICl

Laser induced fluorescence (LIF) spectra of the 3–0 band of the B 3Π0+–X 1Σ+ system of I 35Cl and I 37Cl were observed for the first time by the use of a narrow bandwidth pulsed dye laser. Fluorescence lifetimes of the order of 1 ns have been successfully obtained for the rotational levels in v′=3 of the B 3Π0+ state. These measurements have shown that a new model of curve crossing has to be considered for the predissociation other than the well known B–Y crossing or the recently predicted heterogeneous crossing. On the assumption of Voigt profile for each hyperfine component, the line profile was analyzed to give the quadrupole interaction ‖ΔeQq‖ of approximately 0.065 cm−1 for v′=3. The asymmetry of the type of Fano’s profile was recognized on the observed line profile.

Measurement of Sub-Nanosecond Single-Rovibronic Fluorescence with a Pulsed Dye Laser

A method of fluorescence-decay measurement of sub-nanosecond time-resolution is presented which employs a narrow band pulsed dye laser for molecular excitation and a computer-controlled waveform digitizer for decay-data recording. The kinematical parameters of single rovibronic molecular relaxation are thereby deduced routinely from the observed time-evolution of fluorescence decay through a curve-fitting procedure of convolution-integral treatment. A specimen observation of fluorescing dye solution demonstrates the capability of determining fluorescence decay time as short as 0.2 ns with a precision of better than ±0.05 ns. The method was applied to a systematic single rovibronic observation of fluorescence from the predissociative state of interhalogen molecule.

Computational Design of Solenoid Geometry for Homogeneous On-Axis Field

A recepie is given for the geometry of thick solenoid which produces an on-axis field of high homogeneity over a long distance. The recepie is based essentially on the least-square method for the deviation of the field intensity along the axis. It is reduced to a successive approach to the coil cross section which is unique within a given set of dimensional parameters. The method is used with a digital computer to design a superconducting solenoid.

Correlation between Far-Infrared Laser Oscillations in Deuterium Oxide Vapor

It is observed that the tuning curves of some pulsed laser oscillations with D 2 O molecules are subject to a remarkable periodic modulation in the presence of interaction with other simultaneous laser oscillations. Cascade or competitive correlations are found in the following pairs of laser lines: 33.90 and 74.49 µm, 35.07 and 73.31 µm, 36.31 and 71.95 µm, 61.20 and 71.95 µm, 61.20 and 56.82 µm, 72.20 and 218.5 µm and 73.31 and 84.27 µm. Some characteristics relating to a coupled laser transition are discussed.

Investigation of the optogalvanic effect in a microwave discharge

Laser‐induced perturbations of the electron temperature and the electron density are measured by using a Langmuir probe on several electronic transitions in He, Ne, and Ar under a microwave discharge. The electron density either increases or decreases according to the excitation from the nonmetastable or metastable level, respectively. This is consistent with the previous findings in the conventional experiments of the optogalvanic effect. The corresponding electron temperature always decreases with laser excitation showing that the collisional ionization is the dominant process in the discharge. The intensity of the optogalvanic signals is well interpreted in terms of the laser‐induced variation of these plasma parameters.

Study of Multi-Wavelength Oscillations in an H2O Laser by Rate Equations

The far-infrared laser oscillations in water vapor is described theoretically in the form of rate equations in which the molecular rotation-vibration interaction of either Fermi or Coriolis type is taken into account. The theory is developed for the case of pulsed operation of relatively long duration on the assumption that the rotational relaxation time is much shorter than the duration of the excitation pulse. Theoretical expressions for (1) the output power in the steady state as a function of pumping rate and (2) the start-oscillation condition are given. The effects of multi-wavelength oscillations are also obtained and compared with experimental results.

Undulation in the Output of a Pulsed Water-Vapor Laser

Output waveforms of a pulsed H2O laser are observed with an indium-doped germanium detector. The waveform is subject to a remarkable undulation and its frequency varies with the discharge current and conditions of the resonator rather than with the wavelength of emission. It is found that the undulation is interpreted as the beat between laser oscillations of different transverse modes. Since the maximum electron density of order 1012 cm-3 in the laser tube produces a change in refractive index of order 10-6 in the far-infrared, the radial distribution of the electron density is responsible for the change in beat frequencies between transverse modes. Effects of the electron plasma in the optical resonator are theoretically given and applied to explain the observed results.