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Canadian Journal of Physics

Temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer and for quenching in cesium, induced in collisions with H2, N2, CH4, and CD4

I. N. Siara, R. U. Dubois, L. Krause

Published Feb 1, 1982• 9 citations
Publisher

Abstract

The temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer in cesium, as well as the effective quenching of these states, induced in collisions with H2, N2, CH4, and CD4 molecules have been investigated in a series of sensitized fluorescence experiments over a temperature range 390–640 K. The 72P mixing cross sections are of the order of 10−15 cm2 and exceed by at least one order of magnitude similar cross sections for mixing by collisions with Ne, Ar, Kr, and Xe. The large sizes of the mixing cross sections and their variation with temperature are ascribed to a phenomenon of electronic-to-rotational energy transfer.

DOI
10.1139/p82-029

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62P1/2 ↔ 62P3/2 excitation transfer in cesium, induced in collisions with CH4 and CD4 molecules, has been studied in relation to the temperature of the vapour–gas mixtures. The variation with temperature of the cross section ratio Q(CH4)/Q(CD4) is ascribed to an isotope effect which is interpreted on the basis of the theory of absolute reaction rates.

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Inelastic Collisions between Excited Alkali Atoms and Molecules. VIII. 62P1/2–62P3/2 Mixing and Quenching in Mixtures of Rubidium with H2, HD, D2, N2, CH4, and CD4

I. N. Siara, L. Krause

Excitation transfer between the 62P fine-structure substates in rubidium, induced in inelastic collisions with ground-state molecules, has been studied using techniques of sensitized fluorescence. Rubidium vapor in mixtures with various molecular gases was irradiated with each component of the 2P rubidium doublet in turn, and measurements of sensitized-to-resonance fluorescent intensity ratios yielded the following mixing cross sections Q12(2P1/2 → 2P3/2) and Q21(2P1/2 ← 2P3/2), as well as effective quenching cross sections Q1X(2P1/2 → 2XJ″) and Q2X(2P3/2 → 2XJ″). For collisions with H2: Q12(2P1/2 → 2P3/2) = (41 ± 5) Å2; Q21(2P1/2 ← 2P3/2) = (26 ± 3) Å2; Q1X(2P1/2 → 2XJ″) = (36 ± 9) Å2; Q2X(2P3/2 → 2XJ″) = (31 ± 8) Å2. For HD: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (47 ± 13) Å2; Q2X = (38 ± 10) Å2. For D2: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (28 ± 8) Å2; Q2X = (21 ± 7) Å2. For N2: Q12 = (107 ± 15) Å2; Q21 = (70 ± 10) Å2; Q1X = (128 ± 44) Å2; Q2X = (126 ± 33) Å2. For CH4: Q12 = (38 ± 6) Å2; Q21 = (24 ± 3) Å2; Q1X = (129 ± 41) Å2; Q2X = (114 ± 37) Å2. For CD4: Q12 = (52 ± 7) Å2; Q21 = (34 ± 5) Å2; Q1X = (82 ± 30) Å2; Q2X = (76 ± 22) Å2. An analysis of these results suggests the possibility of resonances with various molecular rotational and vibrational transitions.

Canadian Journal of Physics•Feb 1, 1973•19 citations

Inelastic collisions between excited alkali atoms and molecules. VII. Sensitized fluorescence and quenching in mixtures of rubidium with H2, HD, D2, N2, CH4, CD4, C2H4, and C2.H6

E. S. Hrycyshyn, L. Krause

52P1/2 ↔ 52P3/2 mixing and 52S1/2 ← 52P1/2, 2P3/2 quenching in rubidium, induced in collisions with ground state H2, HD, D2, N2, CH4, CD4, C2H4, and C2H6 molecules, have been investigated using methods of sensitized fluorescence. The rubidium vapor mixed with each of the gases was excited in turn by each component of the rubidium resonance doublet, and the resulting fluorescence, emitted at right angles to the direction of the exciting light, was resolved into the two fine-structure components whose intensity ratios were measured in relation to the gas pressure using photon counting techniques. The measurements yielded the following cross sections for the mixing and quenching collisions.For H2: Q12(2P1/2 → 2P3/2) = 11 Å2, Q21(2P1/2 ← 2P3/2) = 15 Å2, Q10(2S1/2 ← 2P1/2) = 6 Å2, Q20(2S1/2 ← 2P3/2) = 3 Å2.[Formula: see text]The mixing cross sections agree with theoretical values within an order of magnitude.

Canadian Journal of Physics•Nov 15, 1970•95 citations
The temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer in cesium, as well as the effective quenching of these states, induced in collisions with H2, N2, CH4, and CD4 molecules have been investigated in a series of sensitized fluorescence experiments over a temperature range 390–640 K. The 72P mixing cross sections are of the order of 10−15 cm2 and exceed by at least one order of magnitude similar cross sections for mixing by collisions with Ne, Ar, Kr, and Xe. The large sizes of the mixing cross sections and their variation with temperature are ascribed to a phenomenon of electronic-to-rotational energy transfer.
The temperature dependence of cross sections for 52P1/2 ↔ 52P3/2 excitation transfer in rubidium, induced in collisions with CH4, CH2D2, and CD4 molecules, has been investigated using methods of sensitized fluorescence over a temperature range 300–650 K. The cross sections, which are of the order of 30 Å2 and which exceed similar cross sections for collisions with noble gas atoms by at least two orders of magnitude, exhibit an isotope effect which is ascribed to the phenomenon of electronic-to-rotational energy transfer.
The method of sensitized fluorescence has been employed to investigate the [Formula: see text] excitation transfer processes in cesium induced in collisions with ground state cesium atoms. The cesium vapor density was kept sufficiently low to enable the cross sections for the mixing process to be determined under single collision conditions and to ensure that radiation trapping and quenching were negligible. A nitrogen laser pumped dye laser was used to excite the cesium atoms to each of the 72P levels in turn and measurements of the relative intensities of fluorescence yielded the following cross sections: [Formula: see text] These results are consistent with the empirical relationship between the magnitude of the cross sections and the fine structure splitting that has previously been determined for the alkalis.
Excitation transfer between the 62P fine-structure substates in rubidium, induced in inelastic collisions with ground-state molecules, has been studied using techniques of sensitized fluorescence. Rubidium vapor in mixtures with various molecular gases was irradiated with each component of the 2P rubidium doublet in turn, and measurements of sensitized-to-resonance fluorescent intensity ratios yielded the following mixing cross sections Q12(2P1/2 → 2P3/2) and Q21(2P1/2 ← 2P3/2), as well as effective quenching cross sections Q1X(2P1/2 → 2XJ″) and Q2X(2P3/2 → 2XJ″). For collisions with H2: Q12(2P1/2 → 2P3/2) = (41 ± 5) Å2; Q21(2P1/2 ← 2P3/2) = (26 ± 3) Å2; Q1X(2P1/2 → 2XJ″) = (36 ± 9) Å2; Q2X(2P3/2 → 2XJ″) = (31 ± 8) Å2. For HD: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (47 ± 13) Å2; Q2X = (38 ± 10) Å2. For D2: Q12 = (42 ± 5) Å2; Q21 = (27 ± 4) Å2; Q1X = (28 ± 8) Å2; Q2X = (21 ± 7) Å2. For N2: Q12 = (107 ± 15) Å2; Q21 = (70 ± 10) Å2; Q1X = (128 ± 44) Å2; Q2X = (126 ± 33) Å2. For CH4: Q12 = (38 ± 6) Å2; Q21 = (24 ± 3) Å2; Q1X = (129 ± 41) Å2; Q2X = (114 ± 37) Å2. For CD4: Q12 = (52 ± 7) Å2; Q21 = (34 ± 5) Å2; Q1X = (82 ± 30) Å2; Q2X = (76 ± 22) Å2. An analysis of these results suggests the possibility of resonances with various molecular rotational and vibrational transitions.
52P1/2 ↔ 52P3/2 mixing and 52S1/2 ← 52P1/2, 2P3/2 quenching in rubidium, induced in collisions with ground state H2, HD, D2, N2, CH4, CD4, C2H4, and C2H6 molecules, have been investigated using methods of sensitized fluorescence. The rubidium vapor mixed with each of the gases was excited in turn by each component of the rubidium resonance doublet, and the resulting fluorescence, emitted at right angles to the direction of the exciting light, was resolved into the two fine-structure components whose intensity ratios were measured in relation to the gas pressure using photon counting techniques. The measurements yielded the following cross sections for the mixing and quenching collisions.For H2: Q12(2P1/2 → 2P3/2) = 11 Å2, Q21(2P1/2 ← 2P3/2) = 15 Å2, Q10(2S1/2 ← 2P1/2) = 6 Å2, Q20(2S1/2 ← 2P3/2) = 3 Å2.[Formula: see text]The mixing cross sections agree with theoretical values within an order of magnitude.