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Physical Review A

Effective core polarizabilities in Ba high-l Nsnldouble Rydberg atoms

Pierre Camus, S. Cohen

Published Mar 1, 1995• 10 citations
Publisher

Abstract

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 ${\mathrm{Ba}}^{+}$ 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{}${10}^{3}$, 7.05(4)\ifmmode\times\else\texttimes\fi{}${10}^{3}$, 2.95(4)\ifmmode\times\else\texttimes\fi{}${10}^{4}$, 9.39(15)\ifmmode\times\else\texttimes\fi{}${10}^{4}$ in ${\mathrm{a}}_{0}^{3}$ units and the ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}$ values are 1.7(8)\ifmmode\times\else\texttimes\fi{}${10}^{4}$, 1.8(2)\ifmmode\times\else\texttimes\fi{}${10}^{5}$, -1.0(2)\ifmmode\times\else\texttimes\fi{}${10}^{6}$, -1.0(2)\ifmmode\times\else\texttimes\fi{}${10}^{7}$ in ${\mathrm{a}}_{0}^{5}$ units for N=7, 8, 9, and 10, respectively. The ${\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}$ evolution with N is found to follow a ${\mathrm{N}}^{\mathrm{*}6.9(1)}$ 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.

DOI
10.1103/physreva.51.1985

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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+{\mathrm{Ba}}^{+}Ba+ Ns effective dipole \ensuremathαd\ensuremath′{\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}\ensuremathαd\ensuremath′​ and quadrupole \ensuremathαq\ensuremath′{\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}\ensuremathαq\ensuremath′​ polarizabilities. The obtained \ensuremathαd\ensuremath′{\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}\ensuremathαd\ensuremath′​ values are 1.25(5)\ifmmode\times\else\texttimes\fi{}103{10}^{3}103, 7.05(4)\ifmmode\times\else\texttimes\fi{}103{10}^{3}103, 2.95(4)\ifmmode\times\else\texttimes\fi{}104{10}^{4}104, 9.39(15)\ifmmode\times\else\texttimes\fi{}104{10}^{4}104 in a03{\mathrm{a}}_{0}^{3}a03​ units and the \ensuremathαq\ensuremath′{\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}\ensuremathαq\ensuremath′​ values are 1.7(8)\ifmmode\times\else\texttimes\fi{}104{10}^{4}104, 1.8(2)\ifmmode\times\else\texttimes\fi{}105{10}^{5}105, -1.0(2)\ifmmode\times\else\texttimes\fi{}106{10}^{6}106, -1.0(2)\ifmmode\times\else\texttimes\fi{}107{10}^{7}107 in a05{\mathrm{a}}_{0}^{5}a05​ units for N=7, 8, 9, and 10, respectively. The \ensuremathαd\ensuremath′{\mathrm{\ensuremath{\alpha}}}_{\mathrm{d}}^{\ensuremath{'}}\ensuremathαd\ensuremath′​ evolution with N is found to follow a N∗6.9(1){\mathrm{N}}^{\mathrm{*}6.9(1)}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 \ensuremathαq\ensuremath′{\mathrm{\ensuremath{\alpha}}}_{\mathrm{q}}^{\ensuremath{'}}\ensuremathαq\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.
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