The effect of imprisonment of radiation in sodium vapor on the measured lifetime of the
32P states has been investigated in an experiment in which the atoms in the vapor were excited with 10-nsec pulses of resonance radiation and the elapsed times between the exciting and the fluorescent pulses were recorded using a time-to-amplitude converter and kicksorter. At vapor densities below
1010 atoms/
cm3, where there is no multiple scattering, the measured lifetime reaches a constant value of (1.63\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ sec, equal to the natural lifetime of the
32P states. In the density range
109-
1013 atoms/
cm3, the variation of the effective lifetime with the vapor density is in good agreement with the predictions of Milne's theory of radiation trapping; agreement with Holstein's theory is observed only in the range
1012-
1013 atoms/
cm3. The results of a subsidiary Hanle experiment show that a multiply scattered photon of sodium resonance fluorescence loses its original polarization and that, at high sodium vapor pressure, coherence is not preserved.
The effects of imprisonment of resonance radiation in potassium vapor and of collisions between excited potassium atoms and N2, H2, HD, and D2 molecules, on the measured lifetimes of the 42P states, have been investigated by the method of delayed coincidences. The potassium atoms were excited with short pulses of resonance radiation, and the delays between the exciting and fluorescent pulses were measured with a time-to-amplitude converter. At pure potassium densities below 1010 atoms/cm3, the measured lifetimes approach the constant values 27.8 ± 0.8 and 27.6 ± 0.8 ns, corresponding to the natural lifetimes of the 42P1/2 and 42P3/2 states, respectively. At higher densities the effective lifetimes are in satisfactory agreement with the predictions of Holstein's theory. The decrease in the measured decay rates observed upon addition of the diatomic gases yielded cross sections for quenching collisions with N2, H2, HD, and D2 which equal 34.0 ± 2.0 Å2, 9.4 ± 1.3 Å2, 11.9 ± 1.5 Å2, and 8.0 ± 2.0 Å2, respectively.
We present a method to precisely determine the
2D3/2 state lifetime of a single trapped
174Yb+ ion. This method is based on the detection of photons emitted from excited states, where a highly synchronized measurement sequence for laser control and an intensity-alternating sequence for atomic excitation and photon counting are used to minimize systematic errors. This method is easy to implement and is immune to fluctuations of magnetic field, laser intensity, and frequency detuning. Combined with the real-time approach of background photon correction, the radiative lifetime of the
2D3/2 state is determined to be $54.83\ifmmode\pm\else\textpm\fi{}0.18$ ms, which represents an order of magnitude improvement in measurement precision. The accurately determined lifetime sets a benchmark for many-body atomic theories and is particularly useful to determine the coherence time limit of the optical clock.