The radiative lifetime of the
1S0 metastable state of
Xe2+ has been measured with a different type of electrostatic ion trap. The ion trap stores ion beams of a few keV using purely electrostatic fields and provides a large field-free region where the stored ions oscillate. A photomultiplier working in the single-photon counting mode was used to observe the 380 nm photons arising from the magnetic dipole
(M1) transition ${}^{1}{\stackrel{\ensuremath{\rightarrow}}{{S}_{0}}}^{3}{P}_{1}$ of
Xe2+. The present measurement yields a value of $4.46\ifmmode\pm\else\textpm\fi{}0.08 \mathrm{ms},$ which is in good agreement with previous measurements, but is almost four times more accurate.
The lifetimes of the metastable
1s2s2p4P5/2 level of ${\mathrm{He}}^{\ensuremath{-}},$ as well as the lifetime of the average of the
4P3/2 and
4P1/2 levels, have been measured using a new type of ion trap that stores keV ion beams using electrostatic fields only. The use of a pure electrostatic field avoids the complication of magnetic-field-induced mixing effects, which can interfere with the measurement of the spontaneous decay. The measured lifetime for the
4P5/2 state, after correction for decay induced by blackbody radiation, is $343\ifmmode\pm\else\textpm\fi{}10 \ensuremath{\mu}\mathrm{s}.$ This value is consistent with previous experiments, and in excellent agreement with the most recent theoretical calculations. The average lifetime of the
4P3/2 and
4P1/2 is $8.9\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}\mathrm{s},$ which is about 20% lower than the weighted theoretical value.
The radiative lifetime of Li II
21S0 has been measured by counting decay photons versus time from an ensemble of metastable Li ions stored in a simple electromagnetic trap of the Penning variety. The result is ${\ensuremath{\tau}}_{\mathrm{expt}}=503(26)$ \ensuremath{\mu}sec. The error represents one standard deviation from the mean of a series of 34 separate determinations. This result is in agreement with the theoretical value ${\ensuremath{\tau}}_{\mathrm{th}}=513$ \ensuremath{\mu}sec.
A laser-induced fluorescence technique combined with the observation of spontane ous magnetic dipole photons from the highly metastable 2 3 S t state of Li + has been used to measure the radiative lifetime of this state.The ions are created by electron impact on a lithium A. Direct Determination of the Spontaneous Decay Curve .... 18 B. Direct Determination of the Number of Remaining Metastables 20 C. Indirect Determination of the Radiative Lifetime 23 IV.Ion Trap Theory and Performance 29 A. The RF-Quadrupole Ion Trap 29 B. The Ion Detection System 36 C. Ion Trap Performance 43 1.Ion storage 43 2. Ion distribution 50 V.Experimental Methods 56 A. The Vacuum System 56 B. The Lithium Oven and Hot Wire Detector 60 C. The Ion Trap and Electron Gun 62 D. The Magnetic Field 66 1. Detector operation ..... 73 2. Detector calibration 76 6.The Laser and Optical System 81 H.The Computer System 84 1. Timing and control .84 2. Operating and analysis programs 88 VI.Experimental Results 93 A. The Detection of Spontaneous Ml Photons 93 B. The Detection of Laser-Induced Photons 96 C. The Metastable Lifetime and Nonradiative Quenching .... 99 D. Procedures in Measuring the Radiative Lifetime 104 E. Data Reduction and Error Analysis Ill VII.Conclusion 119 Appendix A. Optical Pumping Calculations .121 A. The Magic Angle 121 B. The Optical Pumping Equations 123 C. Results of the Calculations .126 Appendix B. Measurements of the Ion Density Distribution 128 A. The Laser Scanning Technique 128 B. Experimental Results 130 Acknowledgements ....
The natural radiative lifetimes of the 5${\mathit{d}}^{9}
6{\mathit{s}}^{2}$
(2D5/2 and
2D3/2) metastable states of
Hg+ as well as of the 5${\mathit{d}}^{9}
6s{(}^{3}$${\mathit{D}}_{2}$) metastable state of ${\mathrm{Hg}}^{2+}$ have been measured by counting for equal time intervals either the 282-, 198-, or 217-nm photons emitted when the respective metastable ions decay to the ground state. The metastable Hg ions are produced inside a cylindrical electrostatic ion trap by electron bombardment of background Hg vapor maintained at pressures ranging from 4 to 50\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ Torr. The trap consists of a 5.0-cm-diam, 7.5-cm-long cylinder with end caps plus a concentric 0.003-cm-diam central cylinder maintained at a negative potential of 140 V. Following electron impact of the Hg vapor, some of the photons emitted by the decaying metastable ion population are focused onto a narrow-bandwidth interference filter. The photons transmitted by the filter are detected by a photomultiplier tube as a function of time and generate a decay curve. However, the signal detected with the interference filter used to monitor the $^{2}$${\mathit{D}}_{3/2}$ metastable-state population consists of two exponentially decaying components, indicating the presence of another metastable state decaying through the emission of a photon within the bandpass of the filter. The second component is assumed to arise from a cascade originating with the 5${\mathit{d}}^{9}$6s6p (J=9/2) metastable state of
Hg+. Therefore, as dictated by the composition of the photon decay curve, the pressure-dependent decay rates of the metastable states are obtained from a least-squares fit of either a single- or double-component exponential decay to the natural logarithm of the decay curve.Mean decay rates extrapolated to zero pressure of the background Hg vapor using a straight-line least-squares fit, and the inverse of the zero-pressure intercept yields the natural radiative lifetime of the relevant metastable state. Our results for the lifetimes of the
2D5/2,
2D3/2, and J=9/2 metastable states of
Hg+ are 87\ifmmode\pm\else\textpm\fi{}4, 8.8\ifmmode\pm\else\textpm\fi{}0.4, and 60\ifmmode\pm\else\textpm\fi{}6 msec, respectively, while the lifetime of the
Hg2+ (3D2) metastable state is 34\ifmmode\pm\else\textpm\fi{}3 msec.