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The Journal of Chemical Physics

Sensitized fluorescence in crossed atomic beams: Hg(6 3P0,2)+Tl(6 2P1/2)

Lambert C.-H. Loh, Charlotte M. Sholeen, Ronald R. Herm, D. D. Parrish

Published Sep 1, 1975• 4 citations
Publisher

Abstract

A velocity selected Tl beam has been crossed by an electron-bombarded Hg beam which contains a small percentage of the Hg(6 3P) metastable levels (an approximate 5:1 ratio of 3P2:3P0). By means of an interference filter–photomultiplier combination beneath the collision zone, the cross section for excitation of the 5350 Å (7 2S1/2 → 6 2P3/2)Tl fluorescence has been determined to increase monotonically with decreasing relative collision speed, g, approximately as g−s for s=2.0±0.5. Implications of these results for the sensitized fluorescence phenomenon in vapor mixtures of metallic elements are briefly discussed.

DOI
10.1063/1.431532

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Sensitized fluorescence in crossed atomic beams: Hg(6 $sup 3$P$sub 0$,$sub 2$)+Tl(6 $sup 2$P$sub 1$/$sub 2$)

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A velocity selected Tl beam has been crossed by an electron-bombarded Hg beam which contains a small percentage of the Hg(6 $sup 3$P) metastable levels (an approximate 5:1 ratio of $sup 3$P$sub 2$:$sup 3$P$sub 0$). By means of an interference filter--photomultiplier combination beneath the collision zone, the cross section for excitation of the 5350 A (7 $sup 2$S$sub 1$/$sub 2$ $Yields$ 6 $sup 2$P$sub 3$/$sub 2$)Tl fluorescence has been determined to increase monotonically with decreasing relative collision speed, g, approximately as g$sup -$/subs/ for s=2.0plus-or-minus0.5. Implications of these results for the sensitized fluorescence phenomenon in vapor mixtures of metallic elements are briefly discussed.

•Sep 1, 1975•0 citations

Sensitized fluorescence in thallium induced in collisions with Hg(63P1) atoms

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Collisions of the second kind leading to the transfer of excitation between 6 2P1/2 and 6 2P3/2 states in cesium have been investigated by studying sensitized fluorescence in cesium vapor at pressures in the range 2 × 10−6 to 7 × 10−5 mm Hg, which were not accessible previously to such experiments and at which trapping of resonance radiation is virtually absent. The use of an improved fluorescence tube and of high-resolution interference filters in conjunction with a liquid-air-cooled photomultipler tube permitted accurate measurements of extremely low fluorescent light intensities. The total cross sections for the processes 6 2P1/2 → 6 2P3/2 and 6 2P1/2 ← 6 2P3/2 equal 0.64 × 10−15 cm2 and 3.1 × 10−15 cm2 respectively and are in a ratio of 0.20, which agrees well with the value predicted by the principle of detailed balancing.

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SENSITIZED FLUORESCENCE IN VAPORS OF ALKALI METALS: V. ENERGY TRANSFER IN COLLISIONS BETWEEN CESIUM AND INERT GAS ATOMS

M. Czajkowski, D. A. McGillis, L. Krause

The total cross sections for excitation transfer between the 6 2P1/2 and 6 2P3/2 levels in cesium, induced by collisions of the second kind between cesium and inert gas atoms, have been determined using methods of sensitized fluorescence. The experiments were carried out at a cesium vapor pressure of 1 × 10−6 mm Hg, at which there is no trapping of resonance radiation, and over a range of inert gas pressures extending from 1 to 300 mm Hg. The cross sections Q1(2P1/2 → P3/2) and Q2(2P1/2 ← 2P3/2) are as follows: Cs–He: 5.7 × 10−21 and 3.9 × 10−20 cm2; Cs–Ne: 1.9 × 10−21 and 3.1 × 10−20 cm2; Cs–A: 1.6 × 10−21 and 5.2 × 10−20 cm2; Cs–Kr: 8.3 × 10−21 and 18.4 × 10−20 cm2; Cs–Xe: 7.2 × 10−21 and 27.4 × 10−20 cm2. A mechanism for the excitation transfer is suggested, which involves an interaction between the inert gas atoms and the 6 2P electron in cesium, behaving as a free particle.

Canadian Journal of Physics•Jan 1, 1966•31 citations

SENSITIZED FLUORESCENCE IN VAPORS OF ALKALI METALS: IV. ENERGY TRANSFER IN RUBIDIUM–RUBIDIUM COLLISIONS

A. G. A. Rae, L. Krause

Sensitized fluorescence in rubidium vapor has been investigated in order to determine total cross sections for collisions of the second kind between rubidium atoms, leading to the transfer of excitation between the 5 2P1/2 and 5 2P3/2 resonance levels. The experiments were carried out at vapor pressures below 10−5 mm Hg, where there is virtually no imprisonment of resonance radiation. The exceedingly low fluorescent intensities were registered in an automatically programmed sequence of measurements, using photon counting techniques. The cross sections Q1(5 2P1/2 → 52P3/2) and Q2(5 2P1/2 ← 5 2P3/2) equal 53 Å2 and 68 Å2 respectively at 87 °C and 60 Å2 and 72 Å2 respectively at 107 °C. At both temperatures the ratios Q1/Q2 are in agreement with the values predicted by the principle of detailed balancing.

Canadian Journal of Physics•Sep 1, 1965•11 citations
A velocity selected Tl beam has been crossed by an electron-bombarded Hg beam which contains a small percentage of the Hg(6 3P) metastable levels (an approximate 5:1 ratio of 3P2:3P0). By means of an interference filter–photomultiplier combination beneath the collision zone, the cross section for excitation of the 5350 Å (7 2S1/2 → 6 2P3/2)Tl fluorescence has been determined to increase monotonically with decreasing relative collision speed, g, approximately as g−s for s=2.0±0.5. Implications of these results for the sensitized fluorescence phenomenon in vapor mixtures of metallic elements are briefly discussed.
Sensitized fluorescence in crossed atomic beams: Hg(6 sup3sup 3sup3Psub0sub 0sub0,sub2sub 2sub2)+Tl(6 sup2sup 2sup2Psub1sub 1sub1/sub2sub 2sub2)
A velocity selected Tl beam has been crossed by an electron-bombarded Hg beam which contains a small percentage of the Hg(6 sup3sup 3sup3P) metastable levels (an approximate 5:1 ratio of sup3sup 3sup3Psub2sub 2sub2:sup3sup 3sup3Psub0sub 0sub0). By means of an interference filter--photomultiplier combination beneath the collision zone, the cross section for excitation of the 5350 A (7 sup2sup 2sup2Ssub1sub 1sub1/sub2sub 2sub2 YieldsYieldsYields 6 sup2sup 2sup2Psub3sub 3sub3/sub2sub 2sub2)Tl fluorescence has been determined to increase monotonically with decreasing relative collision speed, g, approximately as gsup−sup -sup−/subs/ for s=2.0plus-or-minus0.5. Implications of these results for the sensitized fluorescence phenomenon in vapor mixtures of metallic elements are briefly discussed.
The transfer of excitation from excited mercury atoms to ground-state thallium atoms was investigated using techniques of sensitized fluorescence. A Hg–Tl vapor mixture contained in a quartz cell was irradiated with Hg 2537 Å resonance radiation which caused the mercury atoms to become excited to the 63P1, state. Subsequent collisions between the Hg(63P1) and Tl(62P1/2) atoms resulted in the population of the 82S1/2, 62D, and 72S1/2 thallium states, whose decay gave rise to sensitized fluorescence of wavelengths 3231, 3520, 3776, and 5352 Å. Intensity measurements on the sensitized fluorescence and on the Hg 2537 Å resonance fluorescence, observed at right angles to the direction of excitation, yielded cross sections of 3.0, 0.3, and 0.05 Å2 for collisional excitation transfer from Hg(63P1) to the 82S1/2, 62D, and 72S1/2 states in thallium, respectively. The results are fully consistent with previously determined cross sections for excitation transfer in other binary metallic vapor systems.
Collisions of the second kind leading to the transfer of excitation between 6 2P1/2 and 6 2P3/2 states in cesium have been investigated by studying sensitized fluorescence in cesium vapor at pressures in the range 2 × 10−6 to 7 × 10−5 mm Hg, which were not accessible previously to such experiments and at which trapping of resonance radiation is virtually absent. The use of an improved fluorescence tube and of high-resolution interference filters in conjunction with a liquid-air-cooled photomultipler tube permitted accurate measurements of extremely low fluorescent light intensities. The total cross sections for the processes 6 2P1/2 → 6 2P3/2 and 6 2P1/2 ← 6 2P3/2 equal 0.64 × 10−15 cm2 and 3.1 × 10−15 cm2 respectively and are in a ratio of 0.20, which agrees well with the value predicted by the principle of detailed balancing.
The total cross sections for excitation transfer between the 6 2P1/2 and 6 2P3/2 levels in cesium, induced by collisions of the second kind between cesium and inert gas atoms, have been determined using methods of sensitized fluorescence. The experiments were carried out at a cesium vapor pressure of 1 × 10−6 mm Hg, at which there is no trapping of resonance radiation, and over a range of inert gas pressures extending from 1 to 300 mm Hg. The cross sections Q1(2P1/2 → P3/2) and Q2(2P1/2 ← 2P3/2) are as follows: Cs–He: 5.7 × 10−21 and 3.9 × 10−20 cm2; Cs–Ne: 1.9 × 10−21 and 3.1 × 10−20 cm2; Cs–A: 1.6 × 10−21 and 5.2 × 10−20 cm2; Cs–Kr: 8.3 × 10−21 and 18.4 × 10−20 cm2; Cs–Xe: 7.2 × 10−21 and 27.4 × 10−20 cm2. A mechanism for the excitation transfer is suggested, which involves an interaction between the inert gas atoms and the 6 2P electron in cesium, behaving as a free particle.
Sensitized fluorescence in rubidium vapor has been investigated in order to determine total cross sections for collisions of the second kind between rubidium atoms, leading to the transfer of excitation between the 5 2P1/2 and 5 2P3/2 resonance levels. The experiments were carried out at vapor pressures below 10−5 mm Hg, where there is virtually no imprisonment of resonance radiation. The exceedingly low fluorescent intensities were registered in an automatically programmed sequence of measurements, using photon counting techniques. The cross sections Q1(5 2P1/2 → 52P3/2) and Q2(5 2P1/2 ← 5 2P3/2) equal 53 Å2 and 68 Å2 respectively at 87 °C and 60 Å2 and 72 Å2 respectively at 107 °C. At both temperatures the ratios Q1/Q2 are in agreement with the values predicted by the principle of detailed balancing.