Radiative decay of the Hg(6{sup 3}P{sub 2}) metastable state in rare gases

A. L. Zagrebin, M. G. Lednev

A. L. Zagrebin, M. G. Lednev

Alexander Z. Devdariani, A. L. Zagrebin

Anthony G. Calamai, Charles E. Johnson

The natural radiative lifetimes of the 5${\mathit{d}}^{9}$6${\mathit{s}}^{2}$ ${(}^{2}$${\mathit{D}}_{5/2}$ and $^{2}$${\mathit{D}}_{3/2}$) metastable states of ${\mathrm{Hg}}^{+}$ 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 ${\mathrm{Hg}}^{+}$. 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 $^{2}$${\mathit{D}}_{5/2}$, $^{2}$${\mathit{D}}_{3/2}$, and J=9/2 metastable states of ${\mathrm{Hg}}^{+}$ 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 ${\mathrm{Hg}}^{2+}$ ${(}^{3}$${\mathit{D}}_{2}$) metastable state is 34\ifmmode\pm\else\textpm\fi{}3 msec.

E. Koudoumas, Thomas Efthimiopoulos

Experimental results are presented, related to the saturation mechanisms of the four-wave sum mixing (4-WSM) generation in Hg when a double resonance enhancement is employed, that is, a two photon resonance to the /spl delta//sup 1/S/sub 0/ state followed by the /spl delta//sup 1/S/sub 0/-6p'/sup 3/D/sub 1/ one photon coupling. This coupling is shown to alter the saturation characteristics of the four-wave sum mixing radiation by affecting the two-photon excitation to the /spl delta//sup 1/S/sub 0/ state, reduce the ionization of the Hg atoms by the incoming radiation and create an absorption window for the generated radiation in a region near the autoionizing state by modifying the linear susceptibility.>

Nikolay A. Kryukov, N. P. Penkin, T. P. Reďko