The lifetime and hyperfine structure of the $(6{s}^{2}6p7s) ^{3}{P}_{1}^{\ensuremath{\circ}}$ excited state in lead have been investigated by the technique of level-crossing spectroscopy. The lifetime of the state was determined to be $\ensuremath{\tau}=5.75(20)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. The linewidth of the level-crossing signal was observed to saturate at a "coherence-narrowed" value in agreement with theoretical predictions. The magnitude of this narrowing corresponds to a 27(3)% branching ratio to the ground state. When the branching ratio and the lifetime are combined with the
f(3639A˚):f(4058A˚) oscillator-strength ratio measured by Khokhlov, one may infer the absolute
f values:
f(2833A˚)=0.169(17),
f(3639A˚)=0.040(8),
f(4058A˚)=0.155(31). The high-field level crossing in the hyperfine structure of the first $^{3}{P}_{1}^{\ensuremath{\circ}}$ state of
Pb207 was found to occur at a magnetic field
Hc=4661.1(4) G, which corresponds to a magnetic-dipole-interaction constant $A=8.811(17)\ifmmode\times\else\texttimes\fi{}{10}^{9}$ cps.
The hyperfine structure of the second-excited
D states of
85Rb,
85Rb, and
133Cs has been measured by the method of cascade-radio-frequency spectroscopy and cascade-level crossing. The sign of the magnetic-dipole coupling constant
A is determined by the method of cascade-decoupling and cascade-radio-frequency spectroscopy with narrow-band excitation. Lifetimes $\ensuremath{\tau}$ of some of these states are measured by the cascade-Hanle effect. We find that for
87Rb, $A(5^{2}D_{\frac{3}{2}})=14.43\ifmmode\pm\else\textpm\fi{}0.23$ MHz, $A(5^{2}D_{\frac{5}{2}})=\ensuremath{-}7.44\ifmmode\pm\else\textpm\fi{}0.10$ MHz, $\ensuremath{\tau}(5^{2}D_{\frac{3}{2}})=205\ifmmode\pm\else\textpm\fi{}40$ nsec; for
85Rb, $A(5^{2}D_{\frac{3}{2}})=4.18\ifmmode\pm\else\textpm\fi{}0.20$ MHz, $A(5^{2}D_{\frac{5}{2}})=\ensuremath{-}2.12\ifmmode\pm\else\textpm\fi{}0.20$ MHz; for
133Cs, $A(6^{2}D_{\frac{3}{2}})=16.30\ifmmode\pm\else\textpm\fi{}0.15$ MHz, $A(6^{2}D_{\frac{5}{2}})=\ensuremath{-}3.6\ifmmode\pm\else\textpm\fi{}1.0$ MHz, $\ensuremath{\tau}(6^{2}D_{\frac{3}{2}})=57\ifmmode\pm\else\textpm\fi{}15$ nsec.
The authors report on the two-photon excitation of 1 S 0 and 1 D 2 states in mercury by pulsed ultraviolet dye laser radiation. A time-resolved registration of two-photon-excited fluorescence provided an accurate determination of the radiative lifetimes of the levels 7 1 S 0 to 9 1 S 0 and 6 1 D 2 to 8 1 D 2 . In an external magnetic field Zeeman quantum beats and the zero-field level crossing signal have been observed. Furthermore the authors describe conditions which cause strong emission of amplified spontaneous radiation in transitions between highly excited mercury levels.