Search results for "Isotope effect"
showing 10 items of 61 documents
Potentials for modeling cold collisions between Na (3S) and Rb (5S) atoms
2005
The experimental characterization of the electronic states correlated to the asymptote of ground state Na (3S) and Rb (5S) atoms was expanded by spectroscopic data on $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ state levels using a high resolution Fourier transform spectroscopy technique. The hyperfine splitting of the $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ state levels was partially resolved and analyzed for both $\mathrm{Na}\phantom{\rule{0.2em}{0ex}}^{85}\mathrm{Rb}$ and $\mathrm{Na}\phantom{\rule{0.2em}{0ex}}^{87}\mathrm{Rb}$ isotopomers. Transitions to high lying levels of the $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ and $X\phantom{\rul…
Ground-state hyperfine-structure measurements of unstableEu+isotopes in a Paul ion trap
1997
Hyperfine separations in unstable ${\mathrm{Eu}}^{+}$ ions of mass 148, 149, and 150 have been measured in laser-microwave double-resonance experiments in a Paul ion trap. In spite of the small available quantities of the isotopes, the experimental uncertainties are of the order of ${10}^{\ensuremath{-}8}$ or below, which is of the same order as in earlier measurements on stable isotopes of ${\mathrm{Eu}}^{+}.$ Extensive second-order perturbation calculation is required to obtain coupling constants for magnetic-dipole $(A)$ and electric-quadrupole $(B)$ interactions. The uncertainties are a few times ${10}^{\ensuremath{-}7}$ for $A$ and ${10}^{\ensuremath{-}3}$ for $B.$ The experiments are …
Interpretation of the SolarCa48/Ca46Abundance Ratio and the Correlated Ca-Ti Isotopic Anomalies in the EK-1-4-1 Inclusion of the Allende Meteorite
1985
$\ensuremath{\beta}$-delayed neutron-emission probabilities of neutron-rich S to K isotopes are calculated with nuclear-structure effects taken into account. These results strongly affect predictions made in high-neutron-density astrophysical scenarios for isotopic abundances of several elements. In particular, it is demonstrated that the solar abundance ratio $^{48}\mathrm{Ca}$/$^{46}\mathrm{Ca}$ as well as the correlated Ca and Ti isotopic anomalies can be explained by the same nucleosynthesis process.
Isotope shifts and hyperfine structure in calcium 4snp and 4snf F Rydberg states
2000
Isotope shifts and hyperfine structure have been measured in 4snp 1 P1 and Rydberg states for all stable calcium isotopes and the radioisotope 41Ca using high-resolution laser spectroscopy. Triple-resonance excitation via Rydberg state was followed by photoionization with a CO2 laser and mass selective ion detection. Isotope shifts for the even-mass isotopes have been analyzed to derive specific mass shift and field shift factors. The apparent isotope shifts for 41Ca and 43Ca exhibit anomalous values that are n-dependent. This is interpreted in terms of hyperfine-induced fine-structure mixing, which becomes very pronounced when singlet-triplet fine-structure splitting is comparable to the h…
Isotope shifts and nuclear-charge radii in singly ionizedCa40–48
1992
The isotope shifts in the resonance lines 4${\mathit{s}}_{1/2}$\ensuremath{\rightarrow}4${\mathit{p}}_{1/2,3/2}$ in Ca ii have been measured for the isotopes $^{40\mathrm{\ensuremath{-}}48}\mathrm{Ca}$ by fast-ion-beam collinear laser spectroscopy. Atomic many-body perturbation theory was then used to calculate the electronic factor for the field shift, giving F=-285(3) MHz/${\mathrm{fm}}^{2}$. The estimate of the uncertainty in F is based on the agreement at the level of 1% for the 4s and 4p hyperfine structures obtained using the same wave functions which include core polarization and pair correlation to all orders. The theoretical value is in excellent agreement with the result F=-283(6)…
Experimental studies of the NaRb ground-state potential up to thev″=76level
2002
Laser induced fluorescence spectra of the C {sup 1}{sigma}{sup +}-X {sup 1}{sigma}{sup +} system of {sup 23}Na{sup 85}Rb and {sup 23}Na{sup 87}Rb have allowed vibrational levels of the electronic ground state up to v{sup ''}=76, spanning 99.85% of the potential well to be observed. The ground-state term values have been fitted to a Dunham polynomial expansion, and also to a direct modified Lennard-Jones (MLJ) potential. The analytical MLJ construction allowed us to match previous measured term values for v{sup ''}{<=}30 with long-range behavior of the potential through the intermediate internuclear distance region covered by the present investigation.
Isotope shifts of neutron-deficient gold isotopes with 193?A?190
1985
The isotope shift between197Au (stable) and the radioactive Au isotopes190Au,191Au,192Au and193Au were determined by resonance fluorescence spectroscopy in the 6s2S1/2–6p2P1/2.λ=267.6nm line. The unstable Au isotopes were produced at the ISOLDE mass separator at CERN. The nuclei were investigated semi on-line in a resonance vessel, heated to 1,400°C. The results areδν190,197=−11.12(39) GHz,δν191,197=−9.67(12) GHz,δν192,197=−8.32(15) GHz,δν193,197=−6.29(11) GHz, corresponding to a change of the mean-square charge radius byδ〈r2〉190,197 =0.261(12) fm2,δ〈r2〉191,197=0.227(5) fm2,δ〈r2〉192,197=0.195(5) fm2,δ〈r2〉193,197 =0.148(4) fm2.
Collinear laser spectroscopy of neutron-rich cerium isotopes near theN= 88 shape transition
2003
Laser spectroscopy has been used to measure the isotope shifts of 146Ce and 148Ce relative to 144Ce, Z = 58. The new data, in combination with existing optical data on the stable isotopes and radioactive 144Ce isotope, permits a study of charge radii variations for the even-N Ce nuclei from N = 78 to N = 90. This range covers both the N = 82 shell closure and the N = 88 shape transition region. A marked increase in deformation occurs at N = 88 for elements with Z ≥ 60 but not for those with Z ≤ 56. The new data for Ce (Z = 58) show an intermediate behaviour, resulting in a smooth increase in deformation with Z in the N = 88, 90 region.
Temperature dependence of dynamic, tunnelling and kinetic isotope effects in formate dehydrogenase
2018
The origin of the catalytic power of enzymes has been a question of debate for a long time. In this regard, the possible contribution of protein dynamics in enzymatic catalysis has become one of the most controversial topics. In the present work, the hydride transfer step in the formate dehydrogenase (FDH EC 1.2.1.2) enzyme is studied by means of molecular dynamic (MD) simulations with quantum mechanics/molecular mechanics (QM/MM) potentials in order to explore any correlation between dynamics, tunnelling effects and the rate constant. The temperature dependence of the kinetic isotope effects (KIEs), which is one of the few tests that can be studied by experiments and simulations to shed li…
Relativistic J-dependence of the isotope shift in the 6s-6p doublet of Ba II
1984
The collinear laser-ion beam technique has been used to measure the isotope shift and hyperfine structure in the 6s-6p doublet (4,934A, 4,554A) of Ba II for all seven stable isotopes. The influence of the excited2P1/2 and2P3/2 states on the field shift leads to a difference of 2.5(3)% in the electronicF factors. The specific mass shifts differ by {A′-A} 2.2(3) MHz which corresponds to about 12% of the normal mass shift.