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Physical Review

Effects of Added Gases on the Sensitized Fluorescence Spectrum of a Hg-Tl Mixture

Richard Allen Anderson, Robert H. McFarland

Published Jul 15, 1960• 9 citations
Publisher

Abstract

An investigation of the sensitized fluorescence of a mercury thallium mixture without and with the addition of argon and helium gases is discussed. Data taken without the addition of foreign gases are used to extend the theory of Frish and Karaulinya to a mercury thallium mixture. Relative collision cross sections for the excitation of the thallium energy states, $9^{2}S_{\frac{1}{2}}$, $7^{2}D_{\frac{5}{2},\frac{3}{2}}$, $8^{2}S_{\frac{1}{2}}$, $6^{2}D_{\frac{5}{2}}$, and $6^{2}D_{\frac{3}{2}}$ were calculated for mercury thallium collisions. Data taken with the addition of argon and helium gases are given to indicate the variation of the intensity of the thallium lines as a function of argon and helium gas pressures at one constant thallium and three mercury temperatures. The explanation of the results depends on the role of mercury $6^{3}P_{1}$ excited atoms, metastable atoms, and mercury molecules in collision with thallium atoms for energy exchange, and also requires the use of Winans' partial selection rule and other generally accepted ideas concerning energy transfer, emission, and absorption.

DOI
10.1103/physrev.119.693

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

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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.

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Sensitized Fluorescence in Sodium Induced in Collisions with Hg(63P1) Atoms

M. Czajkowski, George M. Skardis, L. Krause

Collisional transfer of excitation from mercury to sodium was investigated using methods of sensitized fluorescence. A mixture of mercury and sodium vapors at low pressure was irradiated with Hg 2537 Å resonance radiation, producing a population of Hg(63P1) atoms whose inelastic collisions with ground-state sodium atoms resulted in a transfer of excitation energy to close-lying S, P, and D states in sodium. The subsequent decay of these states manifested itself in the emission of a sensitized fluorescent spectrum. Absolute intensity measurements on the components of the spectrum yielded 21 cross sections whose magnitudes range from 0.02 to 38.5 Å2 and which exhibit a pronounced resonance with ΔE, the energy defect between Hg (63P1) and the appropriate level in sodium.

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The Effect of Foreign Gases upon the Relative Intensities of the Mercury Triplet 2P0123−2S13 under Conditions of Optical Excitation

R. T. Macdonald, G. K. Rollefson

Effect of nitrogen and of mixtures of nitrogen and carbon dioxide upon the fluorescence of mercury vapor. By "stepwise" optical excitation, unexcited mercury atoms are raised to the $2^{3}S_{1}$ state. They may leave this level upon the emission of radiation by four paths---the first to the $2^{1}P_{1}$ state, a transition of relatively low probability, and the other three to the $2^{3}P_{2}$, $2^{3}P_{1}$, and $2^{3}P_{0}$ states with the emission of 5461A, 4358A and 4046A, respectively. Measurements, by totally independent methods, of the mean life of the $2^{3}S_{1}$ state yielded values, when measured by the line 5461A, equal to approximately four times those when measured by either 4358A or 4046A. Upon the addition of foreign gas, then, the intensity ratio of 5461A to either 4358A or 4046A should decrease with increasing pressure while that of 4046A to 4358A should remain constant. However, these ratios were all found to be invariant with pressure, up to 400 mm in the case of nitrogen and up to 100 mm in the case of the nitrogen-carbon dioxide mixtures.

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The Metastable 2 p 3 -State of Mercury Atoms

S. Loria

Let us consider a mixture of mercury vapor, thallium vapor and nitrogen in a closed quartz tube under well defined conditions of pressure and temperature, illuminated by λ 2537A of constant intensity. \n \nDue to the absorption of the illuminating radiation a constant number N of mercury atoms will be activated in unit time. Those activated atoms persist in the 2p2-state for a finite time t which is known to be of the order of magnitude of 10^-7 sec [1]. If they escape collision during this period they return to their normal state in the ordinary wave-emitting radiation (resonance). They may, however, while activated, collide with nitrogen molecules, normal mercury atoms or normal thallium atoms. We shall assume, for the present, that the amount of nitrogen and thallium sufficiently exceeds the amount of mercury, so that we may disregard totally the collisions between activated and normal mercury atoms. \n \nWe assume furthermore that all collisions between activated mercury atoms and thallium atoms result in the activation of the latter, producing the fluorescence radiation of thallium with a constant energy distribution between its different lines.

Proceedings of the National Academy of Sciences•Nov 1, 1925•3 citations

Experimental Determination of the De-excitation Cross Section for the 6P13 State of Mercury by Thallium

B. C. Hudson, B. Curnutte

The de-excitation or quenching cross section of thallium for the $6^{3}P_{1}$ state of mercury has been obtained over a range of temperatures of 800 to 900\ifmmode^\circ\else\textdegree\fi{}C. Comparison of the resonance fluorescence from a mercury-thallium vapor mixture with the resonance fluorescence from a pure mercury vapor at the same number density, as determined by line absorption, allows the calculation of the de-excitation cross section. The present data together with Garrett's value of the lifetime of the $6^{3}P_{1}$ state of mercury and existing data on the vapor pressures of mercury and thallium were used to obtain values of the de-excitation cross section. Values of the cross section range from 108\ifmmode\pm\else\textpm\fi{}41 ${\mathrm{\AA{}}}^{2}$ at 800\ifmmode^\circ\else\textdegree\fi{}C to 80\ifmmode\pm\else\textpm\fi{}19 ${\mathrm{\AA{}}}^{2}$ at 900\ifmmode^\circ\else\textdegree\fi{}C. The corresponding quenching-rate coefficients varied from (5.1\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ ${\mathrm{cm}}^{3}$/sec at 800\ifmmode^\circ\else\textdegree\fi{}C to (4.0\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ ${\mathrm{cm}}^{3}$/sec at 900\ifmmode^\circ\else\textdegree\fi{}C.

Physical Review•Aug 5, 1966•6 citations
An investigation of the sensitized fluorescence of a mercury thallium mixture without and with the addition of argon and helium gases is discussed. Data taken without the addition of foreign gases are used to extend the theory of Frish and Karaulinya to a mercury thallium mixture. Relative collision cross sections for the excitation of the thallium energy states, 92S129^{2}S_{\frac{1}{2}}92S21​​, 72D52,327^{2}D_{\frac{5}{2},\frac{3}{2}}72D25​,23​​, 82S128^{2}S_{\frac{1}{2}}82S21​​, 62D526^{2}D_{\frac{5}{2}}62D25​​, and 62D326^{2}D_{\frac{3}{2}}62D23​​ were calculated for mercury thallium collisions. Data taken with the addition of argon and helium gases are given to indicate the variation of the intensity of the thallium lines as a function of argon and helium gas pressures at one constant thallium and three mercury temperatures. The explanation of the results depends on the role of mercury 63P16^{3}P_{1}63P1​ excited atoms, metastable atoms, and mercury molecules in collision with thallium atoms for energy exchange, and also requires the use of Winans' partial selection rule and other generally accepted ideas concerning energy transfer, emission, and absorption.
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.
The excitation transfer cross sections to several of the excited states of thallium from the 63P16^{3}P_{1}63P1​ and 63P06^{3}P_{0}63P0​ states of mercury have been obtained at various temperatures in the range 800\ifmmode^\circ\else\textdegree\fi{}C to 900\ifmmode^\circ\else\textdegree\fi{}C. Analysis of the equilibrium rates of absorption, emission, and collision processes allows the calculation of excitation transfer cross sections from experimentally determined ratios of intensities of thallium-sensitized fluorescence lines to the intensity of mercury resonance fluorescence, using calculated values of the thallium transition probabilities. The values obtained for the excitation transfer cross sections are comparable in magnitude with collision cross sections based on considerations of gas kinetics.
Collisional transfer of excitation from mercury to sodium was investigated using methods of sensitized fluorescence. A mixture of mercury and sodium vapors at low pressure was irradiated with Hg 2537 Å resonance radiation, producing a population of Hg(63P1) atoms whose inelastic collisions with ground-state sodium atoms resulted in a transfer of excitation energy to close-lying S, P, and D states in sodium. The subsequent decay of these states manifested itself in the emission of a sensitized fluorescent spectrum. Absolute intensity measurements on the components of the spectrum yielded 21 cross sections whose magnitudes range from 0.02 to 38.5 Å2 and which exhibit a pronounced resonance with ΔE, the energy defect between Hg (63P1) and the appropriate level in sodium.
Effect of nitrogen and of mixtures of nitrogen and carbon dioxide upon the fluorescence of mercury vapor. By "stepwise" optical excitation, unexcited mercury atoms are raised to the 23S12^{3}S_{1}23S1​ state. They may leave this level upon the emission of radiation by four paths---the first to the 21P12^{1}P_{1}21P1​ state, a transition of relatively low probability, and the other three to the 23P22^{3}P_{2}23P2​, 23P12^{3}P_{1}23P1​, and 23P02^{3}P_{0}23P0​ states with the emission of 5461A, 4358A and 4046A, respectively. Measurements, by totally independent methods, of the mean life of the 23S12^{3}S_{1}23S1​ state yielded values, when measured by the line 5461A, equal to approximately four times those when measured by either 4358A or 4046A. Upon the addition of foreign gas, then, the intensity ratio of 5461A to either 4358A or 4046A should decrease with increasing pressure while that of 4046A to 4358A should remain constant. However, these ratios were all found to be invariant with pressure, up to 400 mm in the case of nitrogen and up to 100 mm in the case of the nitrogen-carbon dioxide mixtures.
Let us consider a mixture of mercury vapor, thallium vapor and nitrogen in a closed quartz tube under well defined conditions of pressure and temperature, illuminated by λ 2537A of constant intensity. \n \nDue to the absorption of the illuminating radiation a constant number N of mercury atoms will be activated in unit time. Those activated atoms persist in the 2p2-state for a finite time t which is known to be of the order of magnitude of 10^-7 sec [1]. If they escape collision during this period they return to their normal state in the ordinary wave-emitting radiation (resonance). They may, however, while activated, collide with nitrogen molecules, normal mercury atoms or normal thallium atoms. We shall assume, for the present, that the amount of nitrogen and thallium sufficiently exceeds the amount of mercury, so that we may disregard totally the collisions between activated and normal mercury atoms. \n \nWe assume furthermore that all collisions between activated mercury atoms and thallium atoms result in the activation of the latter, producing the fluorescence radiation of thallium with a constant energy distribution between its different lines.
The de-excitation or quenching cross section of thallium for the 63P16^{3}P_{1}63P1​ state of mercury has been obtained over a range of temperatures of 800 to 900\ifmmode^\circ\else\textdegree\fi{}C. Comparison of the resonance fluorescence from a mercury-thallium vapor mixture with the resonance fluorescence from a pure mercury vapor at the same number density, as determined by line absorption, allows the calculation of the de-excitation cross section. The present data together with Garrett's value of the lifetime of the 63P16^{3}P_{1}63P1​ state of mercury and existing data on the vapor pressures of mercury and thallium were used to obtain values of the de-excitation cross section. Values of the cross section range from 108\ifmmode\pm\else\textpm\fi{}41 A˚2{\mathrm{\AA{}}}^{2}A˚2 at 800\ifmmode^\circ\else\textdegree\fi{}C to 80\ifmmode\pm\else\textpm\fi{}19 A˚2{\mathrm{\AA{}}}^{2}A˚2 at 900\ifmmode^\circ\else\textdegree\fi{}C. The corresponding quenching-rate coefficients varied from (5.1\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ cm3{\mathrm{cm}}^{3}cm3/sec at 800\ifmmode^\circ\else\textdegree\fi{}C to (4.0\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ cm3{\mathrm{cm}}^{3}cm3/sec at 900\ifmmode^\circ\else\textdegree\fi{}C.