The lifetimes, oscillator strengths, and coherence narrowing of the
(6p8s)3P10 and
(6p7s)1P10 states of
Pb208 were measured in this work by zero-field level-crossing spectroscopy. For the
(6p8s)3P10 state the lifetime $\ensuremath{\tau}=1.26(5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ sec and the absorption oscillator strength for the 2053-\AA{} transition to the ground state was 0.041(8). For the
(6p7s)1P10 state, $\ensuremath{\tau}=4.8(3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec, and the absorption oscillator strength for the 2022-\AA{} transition to the ground state was 0.020(12).
The lifetime, coherence narrowing, and collision broadening of the
72S21 excited state of atomic thallium has been studied by the technique of zero-field level-crossing spectroscopy. The lifetime of the
72S21 state is determined to be 7.55 (0.08) nsec. The full coherence-narrowing effect gave a branching ratio, from
F=0 of
72S21 to the ground state, of 43%. The cross section for thallium-thallium resonance-broadening collisions is ${\ensuremath{\sigma}}_{\mathrm{T}\mathrm{l}\ensuremath{-}\mathrm{T}\mathrm{l}}=\frac{5.38(0.49)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}}{\overline{v}}$
cm2. The effect of 426-torr helium on the thallium lifetime, coherence narrowing, and resonance broadening was also investigated. From the low-thallium-density region the cross section for helium depolarization of the thallium
72S state is ${\ensuremath{\sigma}}_{\mathrm{T}\mathrm{l}\ensuremath{-}\mathrm{H}\mathrm{e}}\ensuremath{\cong}\frac{7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}}{\overline{v}}$
cm2. There is also indication of a buildup of population in the metastable
62P23 thallium state. From the data, the cross section for the process $\mathrm{Tl}(6^{2}P_{\frac{3}{2}})\ensuremath{\rightarrow}\mathrm{Tl}(6^{2}P_{\frac{1}{2}})$ by helium collisions is $\ensuremath{\sigma}\ensuremath{\simeq}1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}21}$
cm2. The Tl branching ratio in the presence of helium is 39%. It was also found that the thallium-thallium resonance-broadening cross section is ${\ensuremath{\sigma}}_{\mathrm{T}\mathrm{l}\ensuremath{-}\mathrm{T}\mathrm{l}}=\frac{4.04(0.32)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}}{\overline{v}}$
cm2 in the presence of 426 torr of helium. In the presence of 113 torr of He, the resonance-broadening cross section was found to be ${\ensuremath{\sigma}}_{\mathrm{T}\mathrm{l}\ensuremath{-}\mathrm{T}\mathrm{l}}=\frac{5.22(0.13)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}}{\overline{v}}$
cm2. In the case of Ar as the buffer gas, ${\ensuremath{\sigma}}_{\mathrm{T}\mathrm{l}\ensuremath{-}\mathrm{A}\mathrm{r}}=\frac{8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}}{\overline{v}}$
cm2.
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 radiative lifetime of the
21P1 and
31P1 state of atomic helium has been measured by the level-crossing technique. In the experiment, a beam of
21S0 metastable atoms was first produced and then excited to the
21P1 or
31P1 state with resonance radiation. The lifetimes were measured by observing the zero-field level-crossing signals in the detected 584- or 537-\AA{} fluorescent radiation when these
1P1 states decayed to the
11S0 ground state. The results are $\ensuremath{\tau} (2^{1}P_{1})=(5.57\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ sec and $\ensuremath{\tau} (3^{1}P_{1})=(1.73\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. These values are in excellent agreement with theory.
As part of a search for suitable materials for coherent quantum operations, relaxation times and hyperfine structure of the $^{1}D_{2}(1)\text{\ensuremath{-}}^{3}H_{4}(1)$ transition in
Pr3+:KY(WO4)2 (0.29 at. %) at 4 K have been obtained using photon-echo and spectral hole burning techniques. The homogeneous linewidth and the effect of excitation-induced dephasing were measured using two-pulse photon-echo techniques. Linewidths of $23.4\ifmmode\pm\else\textpm\fi{}1.0$ and $17.6\ifmmode\pm\else\textpm\fi{}0.9\phantom{\rule{0.3em}{0ex}}\mathrm{kHz}$ were obtained in the absence and presence of an external magnetic field of about 9 mT. The radiative lifetime
(T1) of the
1D2 state was measured to be $43\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{s}$ using time-resolved laser-induced fluorescence and three-pulse photon-echo measurements. The transmission hole spectra were measured and directly yielded the quadrupole level splitting in the
1D2 ($3.77\ifmmode\pm\else\textpm\fi{}0.03$ and $4.58\ifmmode\pm\else\textpm\fi{}0.04\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$) and
3H4 ($17.1\ifmmode\pm\else\textpm\fi{}0.1$ and $33.2\ifmmode\pm\else\textpm\fi{}0.3\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$) states. The spectral hole lifetime due to population redistribution between the ground-state nuclear levels was also determined to be $70\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$. A strong dipole-dipole interaction observed in this crystal opens for potential applications in quantum computing schemes for performing quantum logic operations, but the short dephasing time makes it less useful in data storage applications.
The technique of level-crossing spectroscopy has been used to measure the fine-structure intervals in the
33P state of
4He through the observation of the level crossings at 2277 and 3700 G. The magnetic fields at the crossing points were used in conjunction with calculated
g values to obtain for the $3^{3}P_{0}\ensuremath{-}3^{3}P_{2}$ fine-structure interval the value 8772.552 \ifmmode\pm\else\textpm\fi{} 0.040 MHz (4.5 ppm). These same data yielded for the lifetime of the
33P state the value 97.6 \ifmmode\pm\else\textpm\fi{} 4.5 nsec and for the cross section for coherence-destroying collisions the value $(718\ifmmode\pm\else\textpm\fi{}78)\ensuremath{\pi}{a}_{0}^{2}$.