E. W. Weber

Implantation of impurity ions into He II for optical spectroscopy purposes

Abstract An experimental arrangement for implantation and handling of high densities of alkaline earth ions in He II is described. First results, including mobility measurements of Sr + , Ba + , Zn + and Cd + ions as well as optical detection of Ba + ions, are reported.

Optical pumping of ions in buffer gases

A method for polarizing thermal ions in buffer gases directly by optical pumping is presented in detail. The production and storage of Sr+ (and Ba+) ions in noble gases, their diffusion and relevant collision processes are discussed. An arc discharge hollow cathode for the generation of intense ionic resonance lines is described. The Sr+ (52S1/2) and electron spin polarizations are treated by rate equations. Fitting the solutions to experimental data obtained from transient signals yields an estimate of a few times 103Å2 for the Sr+ion-electron spin exchange cross section.

Hyperfine density shifts of137Ba+ ions in noble gas buffers

Fractional hyperfine density shifts (fds) for137Ba+ (I=3/2) ions are measured by means of direct optical pumping in noble gas buffers. The results for the fds (137Ba+, 6s2S1/2) in units of 10−9/Torr (0 ‡C) (measured at temperatures between 375 and 395 K) are: + 7(7) (He), −74(8) (Ne), −825(80) (Ar), −1 500(200) (Kr), and < −1600 (Xe). These shifts for the137Ba+ ion are considerably more negative than those for the isoelectronic137Cs atom. It is shown that this difference can be explained by taking into account the additional charge induced interaction. The hyperfine splitting frequency of the unperturbed137Ba+ 6s2S1/2 state is extrapolated tov0=8037741.6(6)kHz.

Hyperfine structure measurement of the9Be+ 22s1/2 ground state by optical pumping

Thermal9Be+ (I=3/2) ions are polarized by direct optical pumping in He buffer gas. Observation of⩼gDF=± 1 transitions yields for the hyperfine splitting frequencyvhfs(9Be+, 1s2 2s2S1/2)=1250018(5) kHz. The result is discussed with regard to predictions of recent theoretical calculations and of the Fermi-Segré formula for the ground state hfs of the Li isoelectronic sequence.

Highly polarized Na gas target by optical pumping with cw multi-mode dye laser

Abstract A pure Na gas target of densities NL ⩽ 10 14 atoms/cm 2 is optically pumped with a cw multi-mode dye (Rh 6G) laser of 0.8 to 2.1 GHz variable spectral width. With 200 to 400 mW laser pump power Na 3S electron (and/or nuclear) spin polarizations ⩾95% (⩾75) are achieved for Na densities of 2.5 × 10 13 atoms/cm 2 in magnetic fields of 75 mT (0.1 mT). The degrees of polarization are measured in a relatively simple way by using two σ ± polarized probe beams of the same laser. Application of the method to other atoms and using the target as charge or spin exchange cell to generate intense polarized ionic or atomic beams is discussed.

Optical pumping of Sr+ ions

Abstract The method of optical pumping has been extended to ions. Sr + ions in their ground state 5 2 S 1 2 have been oriented by absorption of circularly polarized light in presence of a buffer gas. Radio frequency transitions have been observed between the Zeeman levels of the even Sr + isotopes.

Multi-mode cw dye laser

An intense, frequency stable, multi-mode, standing wave cw dye laser of variable bandwidth (0.5 to 3 GHz) and large tuning range (>400 GHz) is described. The resonator of 70 to 100 cm length is a symmetric Z-configuration with the dye jet in the center and with a Lyot-filter and one thin etalon as colour and bandwidth selecting and tuning elements. The characteristics of the laser for the dyes C102, Rh101, and DCM, its use for nonlinear plasma spectroscopy of the atomic hydrogen Hα and Hα lines, and possible further applications are discussed.

Precision measurement of the nuclear magnetic dipole moment of175Lu by optical pumping of free Lu+ ions

Nuclear spin polarization in the 4f146s21S0 ground state of175Lu+(I=7/2) ions is achieved by optical pumping with the resonance line (1S0-1P1,λ=261.5 nm). Nuclear magnetic resonance of the free ions in He buffer gas yields for the magnetic dipole momentμ(175Lu)=2.2240(11)μn (with diamagnetic correction). This value can be used for a more accurate determination of the magnetic dipole moments of other Lu isotopes from knownA factor ratios. A comparison with nuclear induction measurements in solids results in the chemical shiftsδ(LuB12)=−23(5)·10−4 andδ(LuSb)= −31(5)·10−4.

Collisional relaxation of ionic2P3/2 excited states in rare gases

Optical pumping with theD2 line is used to study the depolarization of the first excited2P3/2 states of alkaline earth ions and Yb+ ions in collisions with rare gas atoms. The deorientation cross sections for the even isotopes of Ba+ and Yb+ ions are obtained (in units of 10−16 cm2): rare gas He Ne Ar Kr Xeσ1 (Ba+ 6p2P3/2) 79(11) 89(13) 123(18) 152(22) 204(30)σ1 (Yb+ 6p2P3/2) 60(10) 62(9) 107(18) 133(17) 167(37) The cross sections are discussed in comparison with theoretical calculations and those of isoelectronic atoms. The comparison of the2P3/2 relaxation of even and odd (I=3/2) isotopes of Ba+ allows to draw conclusions on the nature of the depolarization interaction.

Saturation spectroscopy of hydrogen 1-011-011-01lines with a multi-mode cw dye laser

With an intense, broadband multi-mode cw dye laser collisional studies of Hα fine-structure resonances with saturated absorption are extended to He buffer gas pressures larger than 30 mbar (0°C). The broadening and shift of the two prominent Hα(2P−3D) transitions are measured in a (He+4% H) gas discharge. The absolute magnitude and the differences in the width of the lines are explained theoretically by different inelastic fine-structure transfer cross sections which can also be deduced from the pressure effect data. Nuclear polarization of hydrogen atoms by Hα optical pumping and polarization transfer to the H(1S) ground state via Ly-α decay and further applications of the multimode laser are discussed.