H. H. Stroke

Hyperfine Structure and Isotope Shift of 30-Year 207 Bi in the 3067-Å Resonance Line*

A 10-m focal length Czerny–Turner monochromator was used to photograph the emission spectrum of 30-year 207Bi in the 3067-A transition to obtain the hyperfine spectrum and the isotope shift with respect to the naturally occurring isotope 209Bi. A procedure was developed for making a low-impurity electrodeless spectral lamp utilizing only nanogram quantities of 207Bi. The radioisotope was produced in a cyclotron bombardment of natural lead, followed by mass separation. Because the nuclear spin, I, of 207Bi is at present unmeasured, the calculated values for the 207Bi magnetic-dipole and electric-quadrupole constants A and B, respectively, and the isotope shift are based on I=92, which is expected on the basis of the nuclear-shell model. The results are ​207Bi A(6p27s⁴P12)=163.8±0.5mKA(6p3⁴S32°)=−14.87±0.06mKB(6p3⁴S32°)=−13.3±5.0mK​207Bi−​209Bi isotope shift=27.3±5.0mK,with the center of gravity of 207Bi on the lower-wavenumber side.

Isotope Shift between 209 Bi and 6.3-day 206 Bi*

The hyperfine structures of 206Bi (6.3 day) and 209Bi (1018 year) have been measured with the use of a 10-m focal-length Czerny–Turner grating monochromator, and the isotope shift between them was obtained. The radioactive isotope 206Bi was produced by proton bombardment of 208Pb. A radiochemical procedure was developed for separating the radioactive bismuth from the lead target and transferring it into an electrodeless lamp. The light source contained about 10 ng of 206Bi. From an analysis of the hfs in the 6p3 S412 and 6p27s P412 states, a value of 121±13 mK was obtained for the 206Bi–209Bi isotope shift in the 3067-A resonance line. The possible effect on this value of perturbations by other isotopes is discussed.

Isotope shifts in the 6p 2 P3 0 -6p7s P31∘ 283.3-nm line of natural lead

The isotope shifts in the 283.3-nm resonance line of natural lead were measured by atomic-beam absorption spectroscopy with a 9.1-m focal-length spectrometer. The spectrum was calibrated internally by the measured 6p7s P31∘ hfs separation of 207Pb [ J.-L. Cojan H. R. Saussereau , C. R. Acad. Sci. Ser. B277, 415 ( 1973)] and by the value calculated from the level-crossing results of Saloman and Happer [ Phys. Rev.144, 7 ( 1966)] and gJ of Rudi-Saussereau et al. [ Opt. Commun.9, 186 ( 1973)]. The isotope shifts relative to 208Pb are −46.6(6), 207Pb center of gravity; −74.5(6), 206Pb; −142(3), 204Pb. The values are in units of 0.001 cm−1, the negative sign indicating a shift to lower wave numbers. The precision is nearly 1 order of magnitude greater than that of previous measurements.

Hyperfine spectrum of207Bi by absorption spectroscopy: Isotope shift systematics in heavy elements

The hyperfine spectrum of 38−y207Bi in the 6p34S3/2−6p2(3P0)7s4P1/2 3,067-Å resonance line was measured by absorption spectroscopy. The207Bi−209Bi isotope shift is 0.0999(20) cm−1. The relative isotope shifts in bismuth are found to follow the general pattern of the even-neutron number isotopes for the isotones withZ=80, 81, 82 and 87. The magnetic dipole and electric quadrupole hfs interaction constants for207Bi,A(4P1/2) =0.1630(3) cm−1 andB(4S3/2)=−0.016(3) cm−1, were obtained. Except for the isotope shift, these more precise values are in agreement with our previous results.

Hyperfine Structure of 209 Bismuth in the 6p 2 (P3 0 )7s P4 12 State

The hyperfine-structure separation of the 6p2(P30)7s P412 state of 209Bi was measured in the 4722-A transition with a grating spectrograph. The measurement was carried out because a precise value was required in our studies of the spectra of radioactive bismuth isotopes. Our result is Δν(P412)=819.5±3.1 mK. It differs from the previously quoted value of 830 mK, and agrees with a recent result of Dickie and Kelly.

Isotope shift of 47-day 203 Hg†

An improved value of the 203Hg–198Hg isotope shift in the 2537 A 3P1–1S0 line of mercury was determined from emission spectroscopy, with mass-separated samples, and from absorption spectroscopy with unenriched pile-produced isotope. The spectroscopic data were analyzed to yield the isotope shift by use of precise hfs interaction constants that we obtained previously from a level-crossing experiment. The new value for the 203Hg–198Hg isotope shift is IS(203–198) = 0.392 ± 0.006 cm−1; 203Hg lies at the lower-wave-number side. The experiment demonstrates the advantages of absorption spectroscopy for samples of low isotopic purity. The application of this technique to work with small samples is also discussed.

Isotope shift of 3 × 10 5 -yr 202 Pb in the 6p 2 ³P 0 −6p7s ³P1° 283.3-nm resonance line

The isotope shift in the 283.3-nm resonance line of mass-separated radioactive 202Pb was measured by absorption spectroscopy with the use of our 9.1-m focal-length Czerny–Turner spectrometer. The value of the shift, relative to 208Pb, is −208(3) × 10−3 cm−1. A signal-averaging scanning technique was used to record the spectrum. Isotonic comparisons with the relative isotope shifts in mercury and thallium indicate a possible effect on the isotope shift of the unpaired proton in thallium.

Emission and absorption measurements of the anomalous cesium principal-series doublet oscillator-strength ratios

The doublet oscillator-strength ratios ρn of the cesium principal series (62S1/2−n2P3/2,1/2) have been measured for principal quantum number n = 7–21. Both emission and absorption spectroscopic measurements were performed with a 9.1-m focal-length spectrometer. The results show that ρn increases monotonically with n. Discrepancies between emission and absorption results are attributed to collisional mixing of the excited-state populations. Oscillator strengths of both fine structure lines were obtained from the absorption measurements. These agree substantially with similar work by Lorenzen and Niemax [ J. Phys. B11, L723 ( 1978)]. Fano X parameters derived from the measured results are found to decrease monotonically with n. The value of X, extrapolated to the ionization potential, is 2.05 ± 0.03, in good agreement with recent laser-excited atomic-beam results of Raimond et al. [ J. Phys. B11, L765 ( 1978)]. This makes unlikely the existence of a pole of ρn in the discrete spectrum, which requires that X have the value 2.

HFS and isotope shift in the atomic spectrum of205Pb

The hfs of205Pb in the 283.3-nm resonance line and its isotope shift (IS) have been measured in absorption with the use of dispersive spectroscopy. A new method for calibration and analysis, when internal standards are not available is described. The results are: hfs interaction constantsA=70.3(5)×10−3 cm−1,B=−0.6(1.1)×10−3 cm−1,205Pb-208Pb IS=−123.9(2.0)×10−3 cm−1. The derived nuclear magnetic dipole moment,μ=0.704(5)μN is in good agreement with values calculated with a nuclear configuration mixing model.

Remarks on the determination of the odd–even staggering parameter in the spectrum of cadmium

From an analysis of the isotope shifts in the Cd 3261, 4678, and 4416 A lines, it is pointed out that a precise determination of the odd–even staggering parameter is limited less by experimental error than by the lack of reliable knowledge of the specific mass effect.