Hideaki Niki

Rotational, fine, and hyperfine analyses of the (0,0) band of the D 3Π–X 3Δ system of vanadium mononitride

The VN molecule has been produced in a molecular beam apparatus using a laser vaporization source and its D 3Π–X 3Δ(0,0) band has been studied by laser‐induced fluorescence at low (∼0.1 cm−1) and sub‐Doppler resolution (∼0.004 cm−1). Lifetimes of single rotational levels of the D 3Π0 component have been measured and interpreted. Rotational, fine, and hyperfine structures in six of the nine subbands possible for a 3Π ← 3Δ transition have been recorded. Both states exhibit a rapid transition from case (a) → case (b) coupling cases, manifested by reversals in the Lande patterns of the hyperfine structure. The data have been reduced to a set of 35 molecular constants using a modified case (aβ) effective Hamiltonian in which two additional magnetic hyperfine parameters are required for each state. The distortions in the hyperfine structure are due almost entirely to second‐order spin–orbit interaction between states arising from the same configuration. Analysis of the derived parameters indicates that the X 3Δ...

Determining repulsive potentials of InAr from oscillatory bound→continuum emission

Oscillatory bound→continuum emission from vibrational levels v’=0–6 of the B(2Σ+) state of InAr onto the repulsive walls of the X 1(2Π1/2), X 2(2Π3/2), and A(2Σ+) electronic states, has been measured. In the B(2Σ+)→X 1(2Π1/2) spectrum, the intensity extrema have been associated with particular extrema and nodes of the radial wave functions of the emitting levels, and the resulting phase vs energy information directly inverted to yield a pointwise potential for the X 1(2Π1/2) state. Analysis of the observed peak heights then showed that on the range 2.9–3.8 A the associated transition moment function is constant. The overlapping of the B(2Σ+)→X 2(2Π3/2) and B(2Σ+)→A(2Σ+) spectra prevents application of the above inversion procedure, but reliable estimates of these two final‐state potentials were obtained by matching quantum mechanical simulated spectra with experiment. The simulations also showed that the transition moment functions associated with all three transitions are of approximately equal strength.

Hyperfine structure and isotope shift measurements on gadolinium levels by laser-induced fluorescence spectroscopy

Abstract Absorption spectra of gadolinium were measured in 560–600 nm wavelength region by means of laser-induced fluorescence spectroscopy using a cw dye laser and an atomic beam. Isotope shifts were obtained for twenty transitions, and hyperfine constants were determined for fourteen states of the configurations of 4f75d6s29D0, 4f75d6s6p 9D, and 4f75d6s6p 9F.

High resolution molecular beam study of the origin band of the B̃ 2Σ+–X̃ 2Σ+ system of yttrium imide

The (0,0,0)–(0,0,0) band of the B 2Σ+–X 2Σ+ system of three isotopomers of yttrium imide (Y14NH, Y15NH, and Y14ND) has been studied by laser-induced fluorescence in a molecular beam apparatus. Rotational, fine, and nuclear magnetic hyperfine structures have been resolved and analyzed. The B 2Σ+(0,0,0) state of Y14NH, Y14ND, and Y15NH is severely perturbed below J=30.5 by eight, three, and two vibronic states, respectively. Although, the nature of these perturbing states can only be speculated upon, their symmetries are either 2Σ or 2Π, and this has made it possible to deperturb the B 2Σ+ state successfully. The spectra can be reproduced within 140 MHz (0.0047 cm−1). The analyses confirm that the molecule is linear in both states with the nuclear arrangement Y–N–H. The bond lengths in the ground X 2Σ+ state and the B 2Σ+ state have been derived to be rY–N=1.877 57(13) A, rN–H=1.0067(10) A, and rY–N=1.8839(43) A, rN–H=1.242(30) A, respectively. The results are compared with the values of ab initio cal...

MAGNETIC FIELD EFFECT ON LASER ISOTOPE SEPARATION BASED ON POLARIZATION SELECTION RULES

Excitation dynamics of atoms by linearly polarized lasers were analyzed for J=2→2→1→0 multistep transition under a magnetic field. The time evolution of the population in each magnetic substate was calculated by solving the rate equations under the condition where the atomic alignment is gradually destroyed by the precession motion of the angular momentum around the magnetic field. Isotopic selectivity in the laser isotope separation based on the polarization selection rules was discussed. It has been found that a relatively small magnetic field may cause a degradation of selectivity in the case of Gd and the magnetic field should be kept as small as the terrestrial magnetic field when the laser polarization is perpendicular to the magnetic field.

Measurement of Hyperfine Structure and Isotope Shift of Transitions in Gadolinium Using Blue Diode Laser

Laser-induced fluorescence spectroscopy using a single-longitudinal-mode diode laser has been applied to investigating isotope shifts and the hyperfine structures of gadolinium in the wavelength region of 400 nm. Six absorption spectra of transitions from the ground and low-lying metastable levels were measured. The isotope shift per unit mass change varied from 0.6 to 1.0 GHz depending on the transition. The hyperfine splitting constants of 157Gd and 155Gd isotopes were determined for the six upper levels of the transitions. The absorption spectrum of the 999–25661 cm-1 transition showed the narrowest spectral width for odd isotopes.

High resolution molecular beam study of the origin bands of the à 2Π–X̃ 2Σ+ and Ã″ 2Π1/2–X̃ 2Σ+ systems of yttrium imide (Y14NH, Y15NH, and Y14ND)

The (0,0,0)–(0,0,0) bands of the A 2Π–X 2Σ+ and A″ 2Π1/2–X 2Σ+ systems of three isotopomers of yttrium imide (Y14NH, Y15NH, and Y14ND) have been studied by laser-induced fluorescence in a molecular beam apparatus. Rotational, fine, and nuclear magnetic hyperfine structures have been resolved and analyzed. The previously studied B 2Σ+−X 2Σ+ (0,0,0)–(0,0,0) bands of the three isotopomers have been reanalyzed. Global fits of all observed bands, in which the ground state has been fitted to a Hamiltonian model, while the excited states have been represented by term values, have been performed for the three isotopomers. Subsequently, the individual bands have been fitted. The ground state parameters have been fixed at the values obtained in the global fits, while the upper states have been fitted to the Hamiltonian models. The (0,0,0) A 2Π state of Y14NH, Y15NH, and Y14ND is severely perturbed. Even though the nature of these perturbing states can only be speculated upon, the introduction of effective pertu...

X‐ray and radioactive measurements in ICF research at ILE Osaka (invited)

The experimental basis and instrumentation for the Gekko XII laser fusion program developed at the Institute of Laser Engineering (ILE), Osaka University are presented. Many diagnostics are in use to evaluate the key parameters of target implosion in an extremely dense, short period region. In this paper, we describe the present status and future planning of these diagnostics, such as x‐ray, radioactive, and reaction particle measurement, because of their importance for fuel ρR determination.

Rapid Analyses of Tiny Amounts of Powder Samples Using Transversely Excited Atmospheric CO2 Laser-Induced Helium Gas Plasma with the Aid of High-Vacuum Silicon Grease as a Binder on a Metal Subtarget

Rapid quantitative analyses of powder samples available in tiny amounts have successfully been conducted by utilizing a transversely excited atmospheric (TEA) CO2 laser-induced He gas plasma. In this study, 4 mg of powder sample was homogeneously mixed with 4 mg of high-vacuum silicon grease and the silicon grease–mixed powder sample (SMP) was painted on a metal surface, which serves as a subtarget. The grease functions to strongly bind the powder and to suppress blow-off of the powder particles. When a TEA CO2 laser (750 mJ, 10.6 μm, 200 ns) was directly focused on the metal subtarget in He gas at 1 atmosphere, a hightemperature He gas plasma was induced, producing a profusion metastable He atoms. It is assumed that the powder particles together with the silicon grease were vaporized to be effectively atomized and excited through metastable He atoms. The result revealed that this technique can be widely employed in the rapid semi-quantitative analyses of powder samples present in minute amounts. A quantitative analysis of loam soil containing different concentrations of Cu was successfully demonstrated, resulting in a good linear calibration curve. The detection limits of Cr and Pb in loam soil were approximately 4 and 13 mg/kg, respectively. Also, we confirmed that this technique can be applied to check the quality of commercial products such as gold film (Au foil), mineral supplement tablets, and prestigious cosmetic powders.

Measurement of Dipole Matrix Element of Atomic Gd Transitions using Rabi Flopping

Dipole matrix elements were measured for two transitions of the gadolinium atom by detecting the laser-induced fluorescence as a function of laser intensity using Rabi flopping. Those values are 2.7×10-19 and 3.0×10-19 esu cm for 9D2-9F2(0–17381 cm-1) and 9D5-9D4(999–17931 cm-1), respectively. Optical Bloch equations for two-level atoms were calculated for each pair of magnetic sublevels, where the effects of inhomogeneous broadening and laser intensity fluctuation were included. Experimental results were well described by this model. This method is very useful for determining a dipole matrix element which is one of the basic parameters for laser isotope separation.