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High-resolution atomic-beam laser spectroscopy has been performed to study Stark effect of Ba atom. Stark spectra have been observed at various electric fields for Ba highly excited states. The scalar polarizability of the transition from 6s5d3D2 to 5d6p3F3 at 728.0 nm and the tensor polarizability of the 3F3 level have been determined for the first time, to be αs = -89.8 (12) kHz/(kV/cm)2 and αt = -133.7 (20) kHz/(kV/cm)2, respectively.

High-resolution laser spectroscopy has been performed for the rare-earth elements as well as Ba by using a tunable diode laser together with a well collimated atomic beam. Hyperfine structures and isotope shifts have been measured for eight transitions in Ba I, Ce I, Sm I, Eu I, Gd I and Yb I. Hyperfine constants A and B have been determined for the 4 f 7 5 d 6 s 6 p 11 F 5 level of 155,157 Gd, and the 4 f 14 6 s 6 p 3 P 2 , 4 f 14 6 s 7 s 3 S 1 levels of 171,173 Yb. The field shifts and 6 s -electron densities at the nucleus have been derived for the studied elements and compared with the Hartree–Fock calculation.

High-resolution atomic-beam laser spectroscopy in Eu I has been performed using a tunable diode laser. The hyperfine structure (hfs) and isotope shift of the 4 f 7 6 s 2 8 S 7/2 –4 f 7 6 s 6 p 10 P 9/2 transition at 686.45 nm have been measured. The hfs constants A and B of 151 Eu and 153 Eu have been determined for the upper state 4 f 7 6 s 6 p 10 P 9/2 , and the hyperfine anomaly has been derived. The Δ F =+2 transitions, normally forbidden, have been induced by applying a magnetic field of approximately 1 G. Their intensity dependences on the magnetic field strength and on the hfs splittings agreed with the first-order perturbation theory, which considers the mixing between the closely lying hfs levels in the ground state.

High-resolution diode-laser spectroscopy has been performed on atomic beams of natural Gd and Dy. Isotope shifts of the even-mass isotopes have been measured for two transitions in Gd I and one transition in Dy I. Specific mass shifts, as well as field shifts, have been derived for transitions of 4 f 7 5 d 6 s 2 –4 f 7 6 s 2 6 p in Gd I, and 4 f 10 6 s 2 –4 f 9 5 d 6 s 2 in Dy I; the specific mass shift is much larger than the normal mass shift. It has been found that the specific mass shift of the 4 f 10 6 s 2 –4 f 9 5 d 6 s 2 transition in Dy I is about one order of magnitude larger than that of the 4 f 7 5 d 6 s 2 –4 f 7 6 s 2 6 p transition in Gd I. This shows that the specific mass shift, related to the correlation effect between electrons, strongly depends on the orbital angular momentum of electrons.

High-resolution laser spectroscopy in Sm I has been performed by using a tunable diode laser together with a highly collimated atomic beam. Hyperfine structures and isotope shifts of Sm isotopes have been measured for four transitions in the wavelength region of 636–687 nm; the largest isotope shift has been observed. Hyperfine constants A and B of 147 Sm and 149 Sm have been determined for six levels. By using the purest s 2 - s p transition with the largest isotope shift, nuclear parameters λ, changes in mean-square nuclear charge radii δ , and nuclear deformation parameters δ have been derived and discussed.

High-resolution atomic-beam diode-laser spectroscopy in Sm I has been performed. Zeeman spectra have been measured for the three optical transitions at different external magnetic fields and well resolved at the magnetic fields of stronger than 6.0 mT. Using the known precise Landé -factors of the ground multiplet, the Landé -factors of the upper 4f66s6p and levels have been determined, and their precision has been improved compared with the reference values.

High-resolution atomic-beam ultraviolet (UV) laser spectroscopy in Dy I and Er I has been performed. Isotope shifts have been measured for two transitions in Dy I and one transition in Er I. Specific mass shifts and field shifts have been derived for the studied transitions, and large differences between the two 4 𝑓 1 0 6 𝑠 2 – 4 𝑓 1 0 6 𝑠 6 𝑝 transitions in Dy I have been found. From the derived specific mass shifts and field shifts, configuration mixing at the upper levels of transitions has been discussed.

A high‐resolution laser spectroscopy system for refractory elements with an argon‐ion‐ sputtering atomic beam source was constructed, and it has been demonstrated that the sputtering method is extremely useful as an atomic beam source for high‐resolution laser spectroscopy to measure hyperfine structures and isotope shifts for refractory elements, such as Hf, Ta, and W. This source produced intense neutral atomic beams of more than 1010 atoms/s for these elements, and the yield was easily controlled by adjusting the argon‐ion current and the acceleration voltage. Resonance linewidths were 32, 66, and 48 MHz for Hf, Ta, and W, respectively, which are sufficient to measure the hyperfine structures and the isotope shifts in optical transitions. With this system, the signal‐to‐noise ratio reached more than 106. In addition, the temperature of the sputtered atoms found was rather low compared to the kinetic energy given to the atoms.

Stark effect of alkali atoms has been studied by means of high‐resolution atomic‐beam laser spectroscopy. A compact electrode apparatus has been developed in order to produce a stable and strong electric field. The Stark shifts and splittings of the D lines have been measured for K, Rb and Cs atoms. The scalar polarizabilities of the K and Rb D1 lines and the scalar and tensor polarizabilities of the K and Cs D2 lines have been determined, providing a crosscheck of the previously reported values.

With a beam of unenriched lanthanum, the hyperfine structure (hfs) of ${}^{138,139}\mathrm{La}$ has been measured for the transition from the ${5d6s}^{2}{}^{2}{D}_{3/2}$ ground state to the $5d6s6p{}^{4}{F}_{5/2}$ level at 675.304 nm by means of atomic-beam diode-laser spectroscopy. Magnetic-dipole (A) and electric-quadrupole $(B)\mathrm{hfs}$ constants of the 0.090% abundant ${}^{138}\mathrm{La},$ as well as those of ${}^{139}\mathrm{La},$ have been determined for the ${5d6s}^{2}{}^{2}{D}_{3/2}$ and $5d6s6p{}^{4}{F}_{5/2}$ levels; this serves as a measurement of hyperfine structure constants A and B for ${}^{138}\mathrm{La}.$ The isotope shift between ${}^{139}\mathrm{La}$ and ${}^{138}\mathrm{La}$ has been obtained for the 675.304-nm transition and change in mean-square nuclear charge radii $\ensuremath{\delta}〈{r}^{2}〉$ derived.

The high-resolution ultraviolet (UV) laser spectroscopy of 27Al has been performed by the frequency doubling of a tunable diode-laser beam together with a collimated atomic beam. Hyperfine structure spectra have been observed for two UV transitions in Al I, namely, 3s23 p2P1/2–3s24s2S1/2 at 394.401 nm and 3s23 p2P3/2–3s24s2S1/2 at 396.152 nm. The hyperfine structure constants A and B of 27Al have been determined for the 3s23 p2P1/2,3/2 and 3s24s2S1/2 levels, and compared with previously reported results.

High-resolution atomic-beam ultraviolet (UV) laser spectroscopy in Gd I has been performed. Isotope shifts have been measured for five UV transitions and hyperfine structure constants of 155 Gd and...

The Stark effect of the 5 s 2 S 1/2 –5 p 2 P 3/2 transition ( D 2 line) of Rb has been studied by high-resolution atomic-beam laser spectroscopy. The splittings of magnetic sublevels of 5 p 2 P 3/2 have been resolved, and the Stark shifts and splittings of the D 2 line have been measured at various electric fields. The scalar polarizability of the D 2 line and the tensor polarizability of the 5 p 2 P 3/2 level have been determined to be α s (5 p 2 P 3/2 ) - α s (5 s 2 S 1/2 ) = 136.95(89) kHz/(kV/cm) 2 and α t (5 p 2 P 3/2 ) = -40.91(38) kHz/(kV/cm) 2 , respectively, by considering the mixing between hyperfine structure levels of 5 p 2 P 3/2 . The precision of α t (5 p 2 P 3/2 ) has been improved by a factor of 2 compared with the previously reported values.

High-resolution atomic-beam ultraviolet (UV) laser spectroscopy in Ti I has been performed. Isotope shifts have been measured for seven UV transitions and hyperfine structure constants of 47 Ti and 49 Ti have been determined for five high-lying levels. Large specific mass shifts and significant field shifts have been derived for the studied transitions; the specific mass shift of the 3 d 2 4 s 2 –3 d 3 4 p transition is quite larger than that of the 3 d 2 4 s 2 –3 d 2 4 s 4 p transition. J dependences of isotope shift have been obtained for the 3 d 2 4 s 4 p 3 F term and are mainly contributed from the specific mass shift.

In the past decades, gadolinium has been the subject of much interest to spectroscopists as it possesses rich optical transitions with various atomic configurations associated with 4f, 5d, 6s, and 6p open electrons. The higher-order effect of the isotope shift (IS), i.e., the crossed-second-order (CSO) effect, has been an interesting subject, which results in the J and term dependences of ISs. From the point view of nuclear laser spectroscopy, understanding of such a CSO effect is indispensable in deriving nuclear information from measured ISs. On the other hand, recent theoretical calculations of ISs using the configuration interaction method and many-body perturbation theory have reached high precision even for heavy elements with a few valence electrons such as Mg, Na, K, and Ca. High-order effects such as the quantum electrodynamic correction and the nuclear polarizability have also been calculated very recently for Li and He. The CSO effects in the ground configurations of Gd I 4f5d6s and Gd II 4f5d6s were studied early and those in the 4f5d6s and 4f6s6p configurations of Gd I with lower excited energies were reported later. The J dependences of ISs in the D and F terms of 4f5d6s6p at energies of about 18000 cm 1 were also measured. These experiments were performed in the visible and nearinfared regions. Recently, IS measurements at wavelengths of about 405 nm have been reported. However, the J dependences of ISs at high-lying levels such as at energies of about 26000 cm 1 have not yet been reported. Such J dependences, particularly for high-lying levels with a possibly strong configuration mixing, will provide a challenge for atomic theoretical calculation. In this paper, we report the high-resolution atomic-beam laser spectroscopy of Gd I in the ultraviolet (UV) region. ISs are measured for seven UV transitions including the previously reported three transitions. The J dependences of ISs in the three atomic configurations, related to high-lying levels, are obtained and discussed. The present experiment was performed using a UV laser beam and an atomic beam. Using a cw frequency doubler (Spectra-Physics WAVETRAIN), a UV laser beam with a wavelength of about 394 nm was obtained by the frequency doubling of a diode-laser beam produced from a commercial tunable diode laser (Newport 2010M). An atomic beam was produced by heating a molybdenum oven using an electronbombardment method and was made to intersect with a laser beam perpendicularly. Fluorescence from the atomic beam was detected with a cooled photon-counting photomultiplier (Hamamatsu R2257P). A confocal Fabry–Perot interferometer (FPI) with a free spectral range of 300MHz was used for relative frequency calibration. The experimental setup is essentially identical to that used in our previous work. Seven transitions in Gd I were studied in this experiment. Figure 1 shows the wavelengths of studied transitions together with atomic configurations, terms and total electronic angular momentums J of their lower and upper levels. These transitions are all from the ground D term of the 4f5d6s configuration, and their upper levels, with energies of about 26000 cm , relate to three configurations of 4f5d6s6p, 4f5d6p and 4f5d6s with four different terms of D, G, G, and G. Figure 2 shows the observed fluorescence spectrum of the 4f 5d6s D3–4f 5d6p G4 transition at 394.263 nm. It can be seen from Fig. 2 that all peaks are clearly observed for even-mass isotopes, including the lowest abundance (0.20%) isotope Gd. For the 395.868, 394.554, 395.337, and 394.180 nm transitions, no peaks of Gd could be observed owing to their weak transition intensities. The full width at half maximum (FWHM) of the peaks is about 23MHz, which is mainly due to the natural width of the upper level of transition and the residual Doppler broadening of the atomic beam. For measured spectra, peak centers were determined from a least-squares fit with a Lorentz function and calibrated with the FPI spectrum. For each transition, measurement was performed about 20 times. Thus, the ISs between evenmass isotopes were obtained and are presented in Table I for the seven transitions studied; the ISs of three transitions were reported in our previous paper. The uncertainties of the measured ISs, 1–6MHz, include the error of peak-center determination, the error of the free spectral range of the FPI (0.046MHz), and the error of linearity correction for frequency scanning. Hyperfine structures of the odd-mass isotopes Gd and Gd are discussed elsewhere. The IS difference between different transitions with identical lower levels yields the IS difference between different upper levels, i.e., the residual IS Tres. For example, the IS difference between the 394.324 and 394.557 nm transitions yields the IS difference between the upper D1 D2 D3 D5 D4 D6 D3 D2 D1 G4 G6 G4 G6

High-resolution atomic-beam laser spectroscopy has been performed to study the Stark effect of K atoms. A compact electrode apparatus has been developed to produce a stable and strong electric field. The Stark shifts of the D 1 and D 2 lines as well as the splitting of the D 2 line have been measured and found to be proportional to the square of the electric field. The scalar polarizability of the D 1 line and the scalar and tensor polarizabilities of the D 2 line have been determined to be α s (4 p 2 P 1/2 ) -α s (4 s 2 S 1/2 )=81.3±2.4 kHz/(kV/cm) 2 , α s (4 p 2 P 3/2 ) -α s (4 s 2 S 1/2 )=93.0±2.5 kHz/(kV/cm) 2 , and α t (4 p 2 P 3/2 )=-27.6±0.7 kHz/(kV/cm) 2 , respectively, providing a crosscheck of the previously reported values.

High-resolution laser spectroscopy has been proved to be a powerful technique to study the isotope shift (IS) and hyperfine structure (hfs). From such study, one can obtain atomic and nuclear information such as atomic configuration, hfs constants, electron density, nuclear moments and charge distribution; those are indispensable for understanding atomic and nuclear structures. Up to now, many studies have been reported in the visible and near-infrared regions. Spectroscopic measurement in the ultraviolet (UV) region has been scarcely performed. The IS, hfs, and even the atomic configuration are not yet well understood for the UV region which corresponds to high-lying atomic levels at about 26000 cm . Spectroscopic data for such high-lying levels would lead to a challenge for the theoretical calculations of many-electron atoms such as Er as successful calculations of the IS have been recently reported for atoms with a few valence electrons such as Li, He, and Mg. The hfs constants of the Er ground state have been precisely measured by using the laser-rf double resonance technique. Isotope shifts and hyperfine structures of some lower-lying levels in the visible region have been measured by means of atomic-beam laser spectroscopy. However, no experiment has been reported yet in the UV region for Er. In this paper, we report high-resolution atomic-beam laser spectroscopy of Er I in the UV region. ISs are measured for four UV transitions and the Er hfs constants are newly determined for two high-lying levels. From the IS, atomic configuration of the energy level at 25159.143 cm 1 has been assigned. The present experiment was performed by using an atomic beam together with a UV laser beam. An atomic beam was produced by using an electron-bombardment heating method. A molybdenum oven with a 1-mm-diameter hole was heated to about 1400 C and the atomic beam was collimated by a 2-mm-diameter aperture at a distance of 30 cm from the oven. A laser beam with a wavelength range of 780–810 nm was produced by using a commercial tunable diode laser with an external cavity system (Newport 2010M). A UV beam with a wavelength range of 390–405 nm was obtained by the frequency doubling of the diode-laser beam using a cw frequency doubler (Spectra-Physics WAVETRAIN). The power of the UV laser beam was about 30 mW for the 20mW diode-laser beam. The laser beam was collimated and crossed the atomic beam perpendicularly. Fluorescence induced by the incident laser beam was collected with a spherical mirror and detected with a cooled photon-counting photomultiplier (Hamamatsu R2257P). An interference filter (40 nm width at 400 nm) was used in front of the photomultiplier and, therefore, the background from the intense oven light was greatly reduced. For relative frequency calibration, the laser light transmitted through a confocal Fabry–Perot interferometer (FPI) with a free spectral range of 300MHz was recorded simultaneously with the fluorescence from the atomic beam. The experimental setup has been partially described elsewhere. Four transitions in Er I were studied in this experiment. Wavelengths of the transitions, atomic configurations and energies of the lower and upper levels are listed in Table I. The 393.701-nm transition is from the ground configuration 4 f 6s to the upper 4 f 5d6s configuration. The 394.442and 395.642-nm transitions are also from the ground configuration 4 f 6s to the upper 4 f 5d6s configuration. For the 397.358-nm transition, however, the configuration of the upper level is not yet known. A typical observed fluorescence spectrum is shown in Fig. 1 for the 393.701-nm transition in Er I. For stable Er, there are five even-mass isotopes, Er, Er, Er, Er, and Er, and one odd-mass isotope, Er. It can be seen from Fig. 1 that peaks are all clearly observed for the evenmass isotopes, including the lowest abundance (0.14%) isotope Er. The full width at half maximum (FWHM) of peaks is about 25MHz. This width is considered to be mainly due to the natural width of the upper level of the transition and the residual Doppler broadening of the atomic beam; the linewidth of the laser is less than 1MHz and its contribution is negligible. A least-squares fit with a Lorentz function was performed for the measured spectra. Thus, peak centers were determined and calibrated with the FPI spectrum. Relative frequencies between peaks, i.e., the ISs, were obtained for the studied transitions. Hfs constants were determined from derived hfs splittings of the level after the assignment of hfs peaks. The uncertainty of the measured IS includes the error of peak-center determination, the error of the free spectral range of the FPI (0.046MHz), and the error of linearity correction for frequency scanning. For each transition, measurements are performed about 20 times and the final uncertainty of the IS is, therefore, about 1–2MHz. Hfs constants A and B of Er were determined for the ground state and the two upper levels of the 393.701and 395.642-nm transitions. For the other two transitions, the spectrum intensities were not strong enough to determine hfs constants. Determined hfs constants are presented in Table II together with the previously reported values for comparison. For the ground state, the present values of constants A and B are in good agreement with the previously reported values and those of the two upper levels are newly determined. Obtained ISs are presented in Table III. For the 395.642nm transition, only one strong peak for the even-mass isotopes was observed and, therefore, the IS was considered to be 0 and its uncertainty to be the FWHM of peaks of about 25MHz. For the 4 f 6s–4 f 5d6s transition at 393.701 nm, the IS was found to be large positive value. For the 4 f 6s–4 f 5d6s transition, the IS at 394.442 nm is Journal of the Physical Society of Japan Vol. 78, No. 1, January, 2009, 015001 #2009 The Physical Society of Japan

High-resolution atomic-beam laser spectroscopy in Gd I and Er I has been performed in the ultraviolet (UV) region. Isotope shifts have been measured for three UV transitions in Gd I and two transitions in Er I. Hyperfine structure constants of 155,157 Gd and 167 Er have been newly determined for two high-lying levels. Specific mass shifts and field shifts have been derived for the 4 f 7 5 d 6 s 2 –4 f 7 5 d 2 6 p and 4 f 7 5 d 6 s 2 –4 f 8 5 d 6 s transitions in Gd I as well as the 4 f 12 6 s 2 –4 f 11 5 d 6 s 2 and 4 f 12 6 s 2 –4 f 11 5 d 2 6 s transitions in Er I. Results show that the specific mass shift strongly depends on the orbital angular momentum of electrons.

High-resolution laser spectroscopy has been performed using a tunable diode laser to measure the hyperfine structure (hfs) and Zeeman shift of two transitions in Y I. The hfs constants A of 89Y were determined for the 4d5s 2 2 D 3/2 and 2 D 5/2 levels, and 4d5s5p 4 F 3/2 and 4 F 5/2 levels; the A values of the 4 F 3/2 and 4 F 5/2 were determined for the first time. Using circular polarizations, the Zeeman spectra were selectively measured and the g factors were determined for the 4d5s5p 4 F 3/2 and 4 F 5/2 levels.

An atomic beam oven of a discharge type is constructed and the performance in populating a metastable state of Yb I is examined. The relative populations of the ground state 4f 146s 21 S 0 and the metastable state 4f 135d6s 2 (7/2, 3/2)5 of Yb I are measured for the first time by the laser-induced fluorescence method. It is found that the population of the metastable state increases with the discharge current and that of the ground state decreases to 30%. The method is also applicable for other elements.