We use delayed field ionization to observe the microwave resonance transitions of Sr from
5snf to
5sng,
5snh, and
5sni. The energies of the $5sn\ensuremath{\ell}$, $\ensuremath{\ell}>3$ states are split by the indirect spin-orbit coupling of the Sr core to the Rydberg electron, producing the
K splittings. From the
K splittings we extract the ionic dipole and quadrupole matrix elements,
⟨5s∣r∣5p⟩=3.65(25)a0 and
⟨5s∣r2∣4d⟩=12(14)a02. From the dipole matrix element we obtain the dipole polarizability of
Sr+. With the dipole polarizability and the quantum defect differences of adjacent
l states, we can determine the
Sr+ quadrupole polarizability. The dipole and quadrupole polarizabilities of
Sr+ are ${\ensuremath{\alpha}}_{d}=86(11){a}_{0}^{3}$ and ${\ensuremath{\alpha}}_{q}=1.1\ifmmode\times\else\texttimes\fi{}{10}^{3}(10){a}_{0}^{5}$, respectively.
We use delayed field ionization to observe the microwave resonance transitions of Sr from
5snf to
5sng,
5snh, and
5sni. The energies of the $5sn\ensuremath{\ell}$, $\ensuremath{\ell}g3$ states are split by the indirect spin-orbit coupling of the Sr core to the Rydberg electron, producing the
K splittings. From the
K splittings we extract the ionic dipole and quadrupole matrix elements,
⟨5s∣r∣5p⟩=3.65(25)a0 and
⟨5s∣r2∣4d⟩=12(14)a02. From the dipole matrix element we obtain the dipole polarizability of
Sr+. With the dipole polarizability and the quantum defect differences of adjacent
l states, we can determine the
Sr+ quadrupole polarizability. The dipole and quadrupole polarizabilities of
Sr+ are ${\ensuremath{\alpha}}_{d}=86(11){a}_{0}^{3}$ and ${\ensuremath{\alpha}}_{q}=1.1\ifmmode\times\else\texttimes\fi{}{10}^{3}(10){a}_{0}^{5}$, respectively.
We present experimental energy-level positions for Ba high-l Nsnl double Rydberg states with N=8 (n=13--15, l\ensuremath{\geqslant}7) and N=9 (n=13--15, l\ensuremath{\geqslant}7). These data as well as previously reported measurements for N=7 (n=12--15, l\ensuremath{\geqslant}5) and N=10 (n=13--15, l\ensuremath{\geqslant}10) are parametrized in order to yield values for the
Ba+ Ns effective dipole ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}$ and quadrupole ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}$ polarizabilities. The obtained ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}$ values are 1.25(5)\ifmmode\times\else\texttimes\fi{}
103, 7.05(4)\ifmmode\times\else\texttimes\fi{}
103, 2.95(4)\ifmmode\times\else\texttimes\fi{}
104, 9.39(15)\ifmmode\times\else\texttimes\fi{}
104 in
a03 units and the ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}$ values are 1.7(8)\ifmmode\times\else\texttimes\fi{}
104, 1.8(2)\ifmmode\times\else\texttimes\fi{}
105, -1.0(2)\ifmmode\times\else\texttimes\fi{}
106, -1.0(2)\ifmmode\times\else\texttimes\fi{}
107 in
a05 units for N=7, 8, 9, and 10, respectively. The ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}$ evolution with N is found to follow a
N∗6.9(1) power law, while calculated static polarizabilities present somewhat lower power dependence. From this small difference it is not possible to appreciate the importance of nonadiabatic effects between the two asymmetrically excited electrons. On the other hand, the larger discrepancies appearing between the calculated static and fitted quadrupole polarizabilities show clear evidence of nonadiabatic effects. Particularly the negative ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}$ sign for N\ensuremath{\geqslant}9 is attributed to the increasing strength of dynamical effects on the Ns core electron caused by the motion of the outer high-l electron. It gives evidence of the increasing importance of nonadiabatic radial correlation between two planetary electrons when the Ns inner electron is sufficiently radially extended to be characterized as an inner Rydberg electron without, nevertheless, any appreciable overlapping with the outer electron.
Millimeter resonances corresponding to single- and double-photon transitions have been observed between Rydberg levels of sodium with principal quantum number
n ranging from 23 to 41. The levels are prepared by laser excitation; transitions are induced by microwaves produced by a backwave oscillator working around 300 GHz; detection is performed through the selective field-ionization technique. Experimental values for quantum defects, fine-structure intervals, and polarizabilities are reported.
The B-spline configuration-interaction method is applied to the investigations of dynamic dipole polarizabilities for the four lowest triplet states (2 3 S, 3 3 S, 2 3 P, and 3 3 P) of the Li + ion. The accurate energies for the triplet states of n 3 S, n 3 P, and n 3 D, the dipole oscillator strengths for 2 3 S(3 3 S) → n 3 P, 2 3 P(3 3 P) → n 3 S, and 2 3 P(3 3 P) → n 3 D transitions, with the main quantum number n up to 10 are tabulated for references. The dynamic dipole polarizabilities for the four triplet states under a wide range of photon energy are also listed, which provide input data for analyzing the Stark shift of the Li + ion. Furthermore, the tune-out wavelengths in the range from 100 nm to 1.2 μm for the four triplet states, and the magic wavelengths in the range from 100 nm to 600 nm for the 2 3 S → 3 3 S, 2 3 S → 2 3 P, and 2 3 S → 3 3 P transitions are determined accurately for the experimental design of the Li + ion.
The fine structure of high-angular-momentum
n=9 and 10 Rydberg states of barium has been measured precisely, using the resonant excitation Stark ionization spectroscopy method. Optical transitions corresponding to $(n,{n}^{\ensuremath{'}})=(10,30)$, (9,17), and (9,20) were induced with a Doppler-tuned
CO2 laser, determining the fine-structure energies corresponding to all
n=9 and 10 levels with $L\ensuremath{\geqslant}6$. The pattern of these fine-structure energies conforms closely with an effective potential model, by comparison with which the dipole and quadrupole polarizabilities of
Ba+ can be determined. Combining our data with earlier measurements made it possible to deduce, in addition, the portion of ${\ensuremath{\alpha}}_{2}$ due to the lowest excited
D state of
Ba+. Our best estimates of these three properties are ${\ensuremath{\alpha}}_{1}=124.30(16){a}_{0}^{3}$, ${\ensuremath{\alpha}}_{2}=2462(361){a}_{0}^{5}$, and ${\ensuremath{\alpha}}_{2}^{0}=1828(88){a}_{0}^{5}$.