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Fluorescence and excitation spectra arising from transitions between excited states of the HgCd exciplex molecule were produced in a mixture of Hg and Cd vapors following pump-and-probe laser excitation. The vapor mixture, contained in a sealed quartz cell, was irradiated by pulsed pump (3261 \AA{}) and probe (4300\char21{}4750 \AA{}) laser beams, delayed by 450 ns relative to one another. The fluorescence bands were recorded with a monochromator, a photomultiplier, and a digitizing oscilloscope controlled by a microcomputer. In addition to the previously reported and analyzed ``blue-band'' fluorescence that can be excited with a single laser, we observed short-lived and structured fluorescence bands as well as the corresponding excitation bands in the blue spectral region, which we assigned to transitions between specific states of HgCd. An analysis of the bands yielded the vibrational constants for some of the states, as well as their relative internuclear equilibrium separations. These results provide an initial basis for the draft of a partial potential-energy diagram consisting of spin-orbit states correlated to the 5 $^{3}$P manifold in Cd.

The high-lying DO + , E1, and G1 spin—orbit states of the HgZn exciplex were excited by pump and probe laser irradiation of a HgZn vapor mixture in a quartz cell. The decays of these states gave rise to UV bound—free and visible bound—bound fluorescence spectra which were recorded with a monochromator, and scans of the probe dye laser produced excitation spectra in the region 4000–4600 A. Four new spectra were recorded and analyzed, yielding molecular constants for the various states. The new data also led to improved assignments of some previously reported HgZn spectra.

The 0 + u (4 1 P) state of Zn 2 was excited near the crossing of the 1 Σ + u (4 1 P) and 3 Π u (4 3 P) states, using pump and probe methods with time resolution. A structured excitation spectrum was observed in the 530–570 nm region and is ascribed to the 3 Π u (4 3 P)← 3 Π g (4 3 P) vibronic transitions. A fluorescence spectrum which was emitted in the 250–306 nm region is believed to arise from the 1 Σ + u →X 1 Σ + g bound—free decay. It consists of a “Condon internal diffraction pattern” whose profile suggests that it was emitted from a high vibrational level ( v ′ = 19) of the 1 Σ + u state.

Fluorescence and excitation spectra of HgCd were studied using pump-and-probe methods of laser spectroscopy with time resolution. A Hg-Cd vapor mixture, contained in a sealed quartz cell at 700 K, was irradiated by consecutive pump and probe dye-laser pulses. The pump radiation produced a population of Cd 5 $^{3}$${\mathit{P}}_{1}$ atoms whose three-body collisions with Hg atoms resulted in the formation of HgCd excimers in the A${0}^{\mathrm{\ensuremath{-}}}$, A${0}^{+}$, and A1 states, correlated with the Cd 5 $^{3}$P+Hg 6 $^{1}$S manifold, which decayed, emitting a previously reported 4600-\AA{} fluorescence continuum. The probe pulses, delayed by 450 ns, excited the excimers to the higher-lying C${0}^{+}$ (Cd 5 $^{1}$${\mathit{P}}_{1}$+Hg 6 $^{1}$${\mathit{S}}_{0}$) state, which decayed to the repulsive X${0}^{+}$ ground state, emitting fluorescence in the 2400\char21{}2650-\AA{} region. We also observed a bound-bound excitation spectrum in the 5800\char21{}7100-\AA{} region. A study of the time evolution of the excimer fluorescence yielded an approximate value for the three-body rate coefficient for HgCd formation, and an analysis of the spectra produced spectroscopic constants for the states involved in the transitions.

Cross sections for 7/sup 2/D/sub 3/2/bold-arrow-left-right7/sup 2/D/sub 5/2/ transfer in Rb, induced in collisions with He, Ne, Ar, and with ground-state Rb atoms, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a noble gas, was irradiated in a glass fluorescence cell with pulses of 660-nm radiation from a N/sub 2/-laser-pumped dye laser, populating one of the /sup 2/D states by two-photon absorption. The resulting fluorescence included a direct component emitted in the decay of the optically excited state and a sensitized component arising from the collisionally populated state. Relative intensities of the components yielded the cross sections for 7/sup 2/D mixing: Q(/sup 2/D/sub 3/2/..-->../sup 2/D/sub 5/2/) = 8.8, 6.5, 10.4, and 30; Q(/sup 2/D/sub 3/2/reverse arrow/sup 2/D/sub 5/2/) = 5.8, 4.0, 6.9, and 18, in units of 10/sup -14/ cm/sup 2/ for He, Ne, Ar, and Rb, respectively. Cross sections for the effective quenching of the /sup 2/D states were also determined.

Cross sections for 7/sup 2/D and 8/sup 2/D fine-structure mixing in Rb, induced by collisions with various ground-state atoms and N/sub 2/ molecules, have been determined using methods of atomic fluorescence. Rb vapor, pure or mixed with a buffer gas, was irradiated in a glass fluorescence cell with pulses of radiation from a N/sub 2/ laser-pumped dye laser, populating a /sup 2/D fine-structure state by two-photon absorption. The resulting fluorescence included a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state. Measurements of relative intensities of the two components in relation to buffer-gas pressure yielded the following cross sections (in units of 10/sup -14/ cm/sup 2/): Q(7/sup 2/D/sub 3/2/..-->..7/sup 2/D/sub 5/2/) = 1 4.1, 15.5, and 10.0; Q(7/sup 2/D/sub 3/2/reverse arrow7/sup 2/D/sub 5/2/) = 9 .0, 10.5, and 6.9, for Kr, Xe, and N/sub 2/, respectively; Q(8/sup 2/D/sub 3/2/..-->..8/sup 2/D/sub 5/2/) = 8 .9, 4.9, 12.4, 24.9, 25.8, 12.1, and 43.1; Q(8/sup 2/D/sub 3/2/reverse arrow8/sup 2/D/sub 5/2/) = 5 .8, 3.2, 9.4, 15.1, 17.6, 8.3, and 28.5, for He, Ne, Ar, Kr, Xe, N/sub 2/, and Rb, respectively. Cross sections for the effective depopulation of the /sup 2/D states weremore » also determined.« less

Publisher Summary There has been a revival of interest in the spectroscopy of Group 2b excimers because of the possibility of laser action in the blue-green spectral region. In the past, various attempts to produce laser action in Hg2 have been unsuccessful because of excited-state absorption from either the upper laser-level or meta stable levels in equilibrium with it. The spectroscopy of the Hg2 excimer has been investigated systematically during recent years using pump method and probe method, and numerous bound excited states and transitions between pump method and probe method have been identified. Analysis of vibrational structures of the fluorescence and excitation bands yielded vibrational frequencies, anharmonicities, energy separations between the electronic states, and relative equilibrium inter nuclear separations. Recent high-resolution laser-spectroscopic studies of mono isotopic Hg 2 produced partial resolution of the rotational structure. Some non-linearity in the line-separations is due to the mode structure of the probe-laser output.

The 460 nm HgZn fluorescence band was excited by pumping a Hg‐Zn vapor mixture in a quartz cell with 307.59 nm laser pulses which populated the 43P1 Zn atomic state. The excited HgZn molecules were formed by collisions of the 43P1 Zn atoms with ground‐state Hg atoms. The resulting HgZn fluorescent band centered near 460 nm had a half‐width of about 80 nm and contained an additional component near 500 nm.

Extensive and previously unknown fluorescence and excitation spectra of the HgZn excimer have been observed and correlated with a potential energy (PE) diagram. The spectra were excited in a HgZn mixture contained in a quartz vapor cell by successive pulses from two dye lasers using pump‐and‐probe methods. A vibrational analysis of the spectra yield the frequencies and anharmonicities for the states involved in the absorption and emission processes.

The continuum fluorescence bands of mercury at 335 and 485 nm have been known for over 50 years and it was recently shown that the 335 nm band is due to the D1u state of Hg2 [1] and the 485 nm band to the (math) state of Hg3 [2], There have also been several more recent reports of absorption and emission bands involving more highly excited states of Hg2 and Hg3 [2,3], which are now being extensively studied in this laboratory using LIF techniques combined with ‘pump and probe’ methods [4]. The fourth harmonic of a Q-switened Nd:YAG laser (266 nm) is focused into a quartz cell containing pure Hg vapor at densities 1017–1019 cm-3, to populate the metastable (math) Hg2 states. These were probed after a delay of 0.1 – 1 us with a second collinear pulse from a dye laser to produce more highly excited Hg2 states; a 5–10 us delay was required to produce similar Hg3 states. The fluorescence emitted in the decay of the various excited states was resolved with a monochromator and its time-evolution was registered with a transient digitizer. In this way we produced numerous fluorescence and excitation spectra whose analysis yielded accurate values of various molecular constants.