G.D. Saksena

Isotope shifts in odd and even energy levels of the neutral and singly ionised gadolinium atom

Abstract Isotope shift studies in the gadolinium spectra have been extended in the region 4140–4535 A. Isotope shift Δσ(156–160) have been measured in 315 lines of the neutral and singly ionised galolinium atom using a recording Fabry—Perot Spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. Some of the Gd I lines studied involve transitions from newly identified high odd levels of 4f 8 6s 6p, 4f 7 5d 6s 7s and 4f 7 5d 3 configurations to low even levels of 4f 8 6s 2 and 4f 7 6s 2 6p configurations. Electronic configurations of the energy levels have been discussed on the basis of observed isotope shifts. In some cases assigned configurations have been revised and probable configurations have been suggested.

Isotope shifts and electronic configurations of some of the energy levels of the neutral gadolinium atom

Abstract Isotope shift Δ T (156–160) have been evaluated for 52 odd and 90 even energy levels of the neutral gadolinium atom from the measurements carried out on 166 lines of the first spectrum in the region 4535–4975 A on a photoelectric recording Fabry-Perot Spectrometer and enriched samples of 156 Gd and 160 Gd. Earlier studies provide data for just two lines in this region. Assignment of electronic configurations to some of the energy levels have been either confirmed or revised; some unassigned levels have been assigned probable configurations. The present study provides, for the first time, isotope shift of the two levels of 4 f 7 6 s 2 7 s configuration of Gd I.

Isotope shift studies in gadolinium spectra

Abstract Isotope shift studies have been carried out in the gadolinium spectrum using a recording Fabry-Perot spectrometer and gadolinium samples enriched in 156 Gd and 160 Gd isotopes. Isotope shifts Δσ(156–160) have been recorded in 134 lines in the region 3930–4140 A. Some of these lines involve the recently identified even configuration 4f 8 5d6s of Gd I and the newly classified transition 4f 8 6s–4f 8 6p of Gd II. From the isotope shift measurements of lines involving the 4f 8 6s–4f 8 6p transition in Gd II, the isotope shift, ΔT (156–160) = 87 mK, has been obtained for the 4f 8 6s configuration. Electronic configurations have been suggested for a number of energy levels and configuration mixing has been pointed out in certain cases.

Isotope shifts and electronic configurations of the odd parity energy levels of singly ionised samarium

Isotope shift ΔT (148–154) has been evaluated for twelve low-lying even and 89 odd parity levels of singly ionised samarium (Sm II) from the isotope shift (IS) studies in 182 spectral lines of Sm II in the 3890–4525 Å region. These studies were carried out on a recording Fabry-Perot spectrometer using eriched isotopes148Sm (96%) and154Sm (98%) excited in liquid nitrogen-cooled hollow-cathodes. Earlier data on isotope shifts are available for only eight lines in this region. It has been found that for a few spectral lines there are errors both in magnitudes and signs of isotope shifts, reported earlier. Most of the 89 odd parity levels of Sm II, for which ΔT values have been evaluated presently, have in literature either no electronic configuration assignments or only tentative assignments. We have suggested the leading configuration for most of these odd levels of Sm II on the basis of ΔT values evaluated in the present studies.

Electronic configurations and isotope shifts of the energy levels of the neutral dysprosium atom

Abstract Electronic configurations of the energy levels of the neutral dysprosium atom have been suggested on the basis of isotope shift studies carried out in the first spectrum of dysprosium using highly enriched isotopes excited in liquid-air-cooled hollow cathode lamps and a photoelectric recording Fabry-Perot spectrometer. Isotope shift Δ T (164-160) have been evaluated for 85 even and 82 odd energy levels. The configurations 4f 9 d6s6p, 4f 9 6p6s 2 and 4f 10 6s6d along with two new configurations 4f 9 5d 2 6p and 4f 10 6p 2 have been assigned to even levels whereas the configurations 4f 9 5d 2 6s, 4f 10 6s6p and 4f 10 5d6p have been assigned to some odd energy levels of the neutral dysprosium atom.

Isotope shifts in the energy levels of the singly ionized neodymium atom

Abstract Isotope shifts Δ T (142–144) have been evaluated for odd and even energy levels of the singly ionised neodymium atom from the measurements carried out in 168 spectral lines in the 3930–5820 A region, employing a recording Fabry-Perot spectrometer and highly enriched isotopes excited in liquid-air cooled hollow cathodes. The electronic configurations 4f 3 5d6s, 4f 3 5d6p and 4f 4 6p could be assigned to some of the energy levels on the basis of the present study.

Determination of crossed-second-order field shift in8 F and6 F terms of 4f 6(7 F)6s configuration of sm+

We report here the experimental evaluation of crossed-second-order (CSO) effects in the field shift of8F and6F terms of 4f6(7F)6s configuration of singly ionised samarium. Our experimental value of CSO field shift difference between8F and6F terms for148Sm and154Sm is −11.8(3.2) mK, which is in good agreement with the theoretical value of −13.8 mK evaluated using known parameters.

Isotope shift studies and electronic configuration assignments to the energy levels of neutral erbium

Abstract Isotope shifts Δ T (170-166) have been evaluated for 54 even and 94 odd energy levels covering almost all the known configurations of the neutral erbium. These Δ T values have been derived from the isotope shift measurements carried out in 159 lines in the region 3900–4605 A using a Fabry-Perot spectrometer and liquid-air-cooled hollow cathode source with highly enriched 170 Er and 166 Er isotopic samples. Electronic configurations assigned to energy levels of Er I by earlier workers have been mostly confirmed and in few cases revisions have been suggested on the basis of observed Δ T values. Probable configurations have been also suggested for unassigned levels of Er I, and a large number of even levels could be assigned to 4 f 11 5 d 6 s 6 p configuration.

Isotope shift studies in the first spectrum of ytterbium

Abstract Isotope shift △σ (172–176) have been measured in 172 lines of the first spectrum of ytterbium in the region 3900–6500 A employing a recording Fabry—Perot spectrometer and highly enriched isotopes excited in liquid-air-cooled hollow cathodes. Out of the 172 lines studied, energy level classifications are available for 167 of them. Isotope shift △T (172–176) of 62 even and 59 odd energy levels of Yb I have been evaluated and their electronic configurations discussed.

EVALUATION OF CHANGES IN MEAN-SQUARE NUCLEAR CHARGE RADII OF STABLE ISOTOPES OF ERBIUM

Isotope shifts involving all the stable even-A isotopes of erbium have been studied in four transitions using optical technique and highly enriched isotopes. The value of change in mean-square charge radii δ〈r2〉 deduced from our studies in 5806.05 Å (f12 s2-f12 sp) transition is in excellent agreement with muonic X-ray value. With negligible specific mass shift (SMS) in 5806.05 Å line, the SMS and field shifts in other lines are compared via King-Plot. In transitions involving change of 4f-electron (e.g., f12s2-f11ds2), large negative SMS value is obtained which is very close to the theoretically predicted value.