Taro Ito

Heat Capacities of 3He and 4He in the Restricted Geometry of Na-Y Zeolite

Heat capacities of 3 He and 4 He adsorbed on Na-Y zeolite, which has regular interconnected channels of diameters only about 10 A, have been measured in the temperature range 0.1–2 K as a function of the adsorbed helium amount n . The results suggest that the helium atoms are bound to Na + cations and to the substrate in the region of n below n ∼8.5 atoms/cage (40% of full channel). The heat capacity of 3 He for n around 12 atoms/cage shows the same characters as 3 He Fermi liquids. It is likely that, in this region of n , the Fermi degeneracy occurs below the lowest temperature of the present study.

Frequency stabilization of an AlGaAs laser using selective reflection spectrum

Abstract The frequency stabilization of an AlGaAs laser by using a selective reflection spectrum is reported for the first time. This technique has the advantages that a periodic pertubation such as the frequency modulation of light is not required, that the system is very simple and compact, and that the size can be miniaturized. Experiments were carried out by using the 85 Rb-D 1 line, and a stability of 2.5×10 -11 was obtained for an averaging time 60 s without laser frequency modulation. The second derivative of the spectrum was also used for the stabilization, and a stability of 8×10 -12 was obtained for an averaging time 100 s.

NMR Study of Hydrogen Adsorbed on Copper-Nickel Alloys

The adsorption states of hydrogen on Cu100-xNix (x=0 ~10) alloys were studied by nuclear magnetic resonance NMR, and the proton resonance shift was found to decrease and the line width to increase with increasing Ni concentration x. Steep changes in the shift and the line width were observed in the range of low Ni concentration (x<1). The decrease in the shift is attributable to the rapid exchange of H adatoms between sites in the Cu environment and sites of Ni or Cu atoms in contact with the Ni atoms. Since H adatoms on the latter sites are spin-polarized by Ni 3d-electrons via conduction s-electrons, their shifts are smaller than those for H adatoms on the former sites.

A Semiquantum Liquid and a New Ordered Phase of ^4He Adsorbed in Y Zeolite

A fluidity and a quantum effect of a new helium 4 system, unsaturated 4 He adsorbed in a narrow void channel of Y-zeolite crystal, have been studied by measuring the heat capacity. In the case of the quantity adsorbed n =0.445 ×10 -3 mol/g, the heat capacity C is proportional to the temperature, i.e. C = n α T , in the condition T c (=3.25 K)\( \leqq T \lesssim 9\) K, and it reduces suddenly below T c . The coefficient α is 2.2 J/K 2 /mol. The experimental result shows that the state above T c is a semiquantum liquid such as bulk 4 He which remains liquid to much lower temperatures than the Debye temperature. Below T c , the result indicates the presence of an ordered state.

Shift of Na NQR Frequency in NaClO_3 by Nonresonant RF Photon Dressing

The shift of the NQR frequency has been observed for Na in NaClO 3 by applying a nonresonant rf magnetic field and the results are well explained by the theory of a dressed atom.

Accumulative Transfer of Transverse Magnetic Moment between Spin-Locked Rb and Cs Atoms

We propose an efficient method of collisional transfer of transverse magnetic moment between different kinds of atoms using the spin-locking technique. Demonstrating experiments with a rotating or an oscillating rf field are carried out on a 85 Rb– 133 Cs vapor, and the transfer of a large amount of the transverse magnetic moment is observed when the amplitude H 1 of the rf field is comparable to the static magnetic field strength H 0 . The H 1 -dependence of the transfer, in the case of the oscillating rf field, is not simple, because of the Bloch-Siegert shift and associated resonance effects. The transfer of the transverse magnetic moment under the strong rf field is numerically analyzed with the Bloch equations for 85 Rb and 133 Cs coupled through spin-exchange collisions.

Noise Spectroscopy of K Atoms with a Diode Laser

There has been much interest in the influence of the laser noise on the atomic system. So far theoretical works have been performed on calculation of the mean values and the variance of the fluctuated atomic populations, and verified through observation of the fluctuating resonance fluorescence from the atomic vapors. Yabuzaki et al. have observed the excess intensity noise of the resonant light from a diode laser propagated through alkali atomic vapor. They have measured the intensity power spectrum of the light when the laser was tuned near the D2 line of Cs and observed all corresponding hyperfine-splitting resonances in the excited state and Zeeman splitting resonances within a hyperfine level of the ground state. Walser et al. have theoretically studied the intensity fluctuation of laser light propagated through a weakly absorbing medium. The calculated power spectrum of a phase-diffusing field has been found qualitative agreement with the experimental results by Yabuzaki et al. on hyperfine-splitting resonances. Recently, Mitsui has reported a new type of noise spectroscopy with a highly stabilized diode laser. He has investigated the spontaneous noise appeared in optical detection of magnetic resonance of Rb atoms. In this note we report the first observation of hyperfine spectra in the ground state of K and K appearing as the intensity fluctuation at hyperfine splittings of 462MHz and 254MHz of circularly polarized light from a diode laser transmitted through a sample cell. We have also observed the Zeeman hyperfine spectra of K in a static magnetic field. We show that the spectra are strongly dependent of the direction of the static magnetic field. Their splittings as functions of the strength of static magnetic field are compared with the Breit–Rabi formula. The experimental apparatus is quite simple as shown in Fig. 1. The diode laser used was an ordinary Fabry–Perot type with output power of 5mW, operating near the D1 line (769.9 nm) of K atoms. The output of the laser was circularly polarized and applied to a cell containing K vapor at a temperature 90 C, corresponding atomic density to be about 1:15 10 cm 3. The transmitted light was detected by an avalanche photo-diode having frequency response up to 1GHz. The output of the photo-diode was applied to a rf frequency analyzer to obtain the power spectrum of the fluctuation of the transmitted light intensity. A static magnetic field is provided by two pairs of Helmholtz coils mutually perpendicular and about 90 cm in diameter. The strength of the magnetic field is calibrated by using magnetic resonance signals of optically pumped Rb atoms. Figure 2 shows the frequency spectrum of the intensity fluctuation of transmitted light observed when the laser was tuned to the transition from the state F 1⁄4 1 in the ground state to the state F0 1⁄4 1 in the excited state by adjusting the driving current of the laser diode. Sharp resonance signals can be seen at the hyperfine splittings of K and K, 462 and 254MHz, respectively, on the background of broad noise spectrum. When a weak static magnetic field H0 is applied to the K vapor, the hyperfine spectra of K splits into several lines (the effective gyro-magnetic ratio of K is known to be 1⁄4 2 700 kHz/G). Figures 3(a) and 3(b) show the observed Zeeman hyperfine spectra of K for

Transfer of Nutating Spin Polarizations between Rb and Cs Atoms

The transfer of nutating spin polarizations between 85 Rb and 133 Cs atoms is observed for the first time. Maximum transfer occurs when the nutation frequencies are made equal in the rotating frames. The nutating spin polarization of 85 Rb atoms is generated by the periodic excitation of the pumping light and the spin polarization transferred to 133 Cs is observed through the Faraday rotation of a probe beam. The observed time evolutions of the spin polarizations are found to be in good agreement with the results of theoretical calculations based on the Bloch type equation of motion including the effects of optical pumping and spin exchange collisions.

Spin-polarization by optical pumping with selective reflection

A new optical pumping scheme utilizing selective reflection is proposed and studied for the first time. This method enables us to observe the spin-polarization of atoms even at the high density, at which the pumping beam cannot be transmitted through a sample cell. Theoretical analysis shows that the light reflectivity at the glass-vapor interface is strongly dependent on the direction of the macroscopic magnetic moment of optical pumped atoms. Two types of demonstrating experiments are carried out with Cs and Rb vapors at the temperature ∼ 200°C. In the transverse pumping experiment with a modulated laser beam, asymmetry of the magnetic resonance signal with respect to the inversion of the magnetic field direction is observed as predicted by the theory. In the longitudinal pumping experiment, the transfer of a large amount of the magnetic moment by spin-exchange collisions is directly observed.

Effects of nonresonant rf photon dressing on NQR in NaClO3

Abstract Splittings and shifts of Na NQR frequencies and lengthening of T2 of Cl NQR due to nonresonant photons in a mixed mode are observed in NaClO3 and interpreted by using the theory of dressed atoms.