Over a two-year duration, we have compared the frequency of the 199Hg+ 5d(10)6s (2)S(1/2)(F=0)<-->5d(9)6s(2) (2)D(5/2)(F=2) electric-quadrupole transition at 282 nm with the frequency of the ground-state hyperfine splitting in neutral 133Cs. These measurements show that any fractional time variation of the ratio nu(Cs)/nu(Hg) between the two frequencies is smaller than +/-7 x 10(-15) yr(-1) (1sigma uncertainty). According to recent atomic structure calculations, this sets an upper limit to a possible fractional time variation of g(Cs)(m(e)/m(p))alpha(6.0) at the same level.

A phenomenon observed in a simple experiment with a diode laser is found to be a basis for a powerful spectroscopy. In this spectroscopy, the laser frequency is neither scanned nor modulated. Highresolution spectra in a wide radio-frequency range, such as Zeeman and hyperfine spectra in both of the ground and the excited states, are observed simultaneously by frequency analyzing the intensity fluctuation of the light transmitted through a sample cell. Demonstrating experiments are carried out with respect to the D\ and Di lines of Cs and Rb atoms.PACS numbers: 32.80. Bx, In this paper, we report on a new type of highresolution spectroscopy with a diode laser, which is considerably different from other spectroscopic methods developed so far. Above all, the optical system is extremely simple; it consists simply of a diode laser, a sample cell, a fast photodetector, and a radio-frequency spectrum analyzer. In this spectroscopy, it is unnecessary to scan or modulate the laser frequency externally in order to get atomic spectra. It is enough to tune the laser frequency roughly to the Doppler-broadened absorption line. Atomic spectra in the frequency range from tens of kHz to several GHz, such as Zeeman and hyperfine spectra in both of the ground and the excited states, can be obtained by frequency analyzing the intensity fluctuation of the light transmitted through the atoms.This spectroscopy is based on the characteristics of a diode laser. First, the output amplitude of a diode laser is generally very stable, compared with other lasers. As recently shown by Machida, Yamamoto, and Itaya [1], the amplitude fluctuation becomes less than the shot-noise limit, i.e., the output is amplitude squeezed, when it is driven by a constant-current source. On the contrary, the frequency fluctuates at random, i.e., with a very short correlation time, which results in a broad spectral line, the half-width being typically tens of MHz but the wing extending up to several GHz from the line center.In the course of simple absorption spectroscopy of alkali vapor with a diode laser, we found that the stable intensity of the diode laser beam became quite noisy when it was transmitted through the vapor. Such excess noise has also been observed by Haslwanter et al. [2] and Ritsch, Zoller, and Cooper [3]. The noise amplitude becomes maximum when the laser frequency is resonant with the atomic absorption lines. Figure 1 shows the intensity change of the light transmitted through Cs atoms, observed when the laser frequency was scanned slowly through the absorption line from the F=4 level in the ground state to the 6/* 1/2 state. One can see that the noise amplitude is very large at resonance, larger than the change of the average light intensity. Since the output of the diode laser was still very stable even in such a case, we found that the intensity noise was not due to the insta-bility of the diode laser by the feedback of the laser light or spontaneous emission from atoms. We found in this way that the intensity fluctuation in the transmitte...

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We report a linear surface-electrode trap that can be used to form parallel ion strings. By adjusting the balance of the radio-frequency (RF) voltages applied to central and RF electrodes, the RF pseudopotential can be varied from single-well to double-well in the radial direction. Ions located on two parallel lines of the RF potential null are in principle free from excess micromotion if appropriate static voltages are applied. Calcium ions were trapped for the evaluation of the designed electrode. An ion string in the single-well potential and two ion strings in the double-well potential were observed by changing the RF voltages. Such traps could be used for quantum simulation of coupled spin systems.

We report a surface electrode trap with a relatively large trap depth (0.6-1.0 eV). The trap electrodes are formed by gold plating an alumina substrate. Calcium ions are trapped approximately 400 µm above the trap surface. We demonstrate micromotion compensation based on parametric resonance for surface electrode traps. Unlike the conventional method based on radio-frequency (rf)-photon correlation in which the wave vector of the laser beam must have a component parallel to the micromotion to be detected, the proposed method is independent of the laser propagation direction. This enables the micromotion component normal to the electrode surface to be detected without increasing the scattered light.

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