Wei-Guo Jin

High-Resolution Diode-Laser Spectroscopy of the Rare-Earth Elements

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.

Specific Mass Shift in Gd I and Dy I

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.

Isotope Shifts in Gd I and Er I by UV Laser Spectroscopy

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.

A laser ion source with a thin ohmic-heating ionizer for the TIARA-ISOL

Abstract An ohmic-heating laser ion source with a thin ionizer of thickness of 30 μm has been developed for the TIARA-ISOL. It can form an electric field of 4–5 V/cm inside the ionizer. The properties of the laser ion source were tested on- and off-line with aluminum isotopes. The FWHM of the time distribution of the bunched photoions from the ion source was about 4 μs for 27Al. In on-line experiment, a photoionization efficiency of about 0.1% for 25Al was obtained.

Measurement of Stark Shift of Potassium D Lines

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.

Stark Effect of the Rubidium D2 Line Studied by High-Resolution Laser Spectroscopy

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.

Hyperfine Structure of 27Al by High-Resolution Ultraviolet Laser Spectroscopy

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.

J Dependence of the Isotope Shift in the Gd I 4f76s26p9P Term

High-resolution laser spectroscopy in Gd I has been performed using a tunable diode laser. Isotope shifts of the even-mass isotopes have been measured for two transitions from the 4f75d6s29D4 and 9D5 levels to the 4f76s26p9P3 and 9P4 levels in Gd I. The J dependence of the isotope shift, related to the crossed-second-order (CSO) effect, has been obtained for the 4f76s26p9P3 and 9P4 levels. The CSO parameter z6p of the 4f76s26p configuration has been estimated for the first time.

Hyperfine Structure and Isotope Shift in High-Lying Levels of Gd I

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...

J Dependence of Isotope Shifts at High-Lying Levels of Gd I

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