Hyperfine-structure investigation of highly excited D2 levels in Rb87 and Cs133 using a cw tunable dye laser in a two-step excitation scheme

Abstract

The hyperfine structure of several highly excited $^{2}D$ states in $^{87}\mathrm{Rb}$ and $^{133}\mathrm{Cs}$ has been measured. The $D$-state atoms were produced in a two-step-excitation process. In the first step, multiple scattering of the strong alkali-metal ${D}_{1}$ and ${D}_{2}$ lines from an rf lamp was used to excite atoms into the first excited $^{2}P$ levels. The intense tunable radiation from a cw dye laser was used in the second step to transfer $P$-state atoms into highly excited $D$ states. Level-crossing and optical-double-resonance techniques were used for the determination of the absolute values of the hyperfine-interaction constants. The following results (in MHz) were obtained for the magnetic dipole and the electric quadrupole interaction constants $a$ and $b$: For $^{87}\mathrm{Rb}$, $|a(6^{2}D_{\frac{3}{2}})|=7.84(5)$, $|b(6^{2}D_{\frac{3}{2}})|=0.53(6)$ ($\frac{b}{a}>0$), $|a(^{2}D_{\frac{5}{2}})|=3.6(7)$, $|a(7^{2}D_{\frac{3}{2}})|=4.53(3)$, $|b(7^{2}D_{\frac{3}{2}})|=0.26(4)$ ($\frac{b}{a}>0$), $|a(7^{2}D_{\frac{5}{2}})|=2.2(5)$. For $^{133}\mathrm{Cs}$, $|a(8^{2}D_{\frac{3}{2}})|=3.98(8)$, $|a(8^{2}D_{\frac{5}{2}})|=0.9(4)$, $|a(9^{2}D_{\frac{3}{2}})|=2.37(3)$, $|a(9^{2}D_{\frac{5}{2}})|=0.5(2)$, $|a(10^{2}D_{\frac{3}{2}})|=1.52(3)$, $|a(10^{2}D_{\frac{5}{2}})|=0.4(2)$. The $a$ factors generally deviate strongly from the values expected in a one-electron picture of the alkali-metal atom indicating the importance of polarization and correlation effects for these states. For $^{87}\mathrm{Rb}$ a comparison with a recent calculation including polarization effects is made. The $b$ factors for $^{87}\mathrm{Rb}$ are the first significant values allowing a calculation of an alkali-metal-atom nuclear quadrupole moment from non-$P$-state data.