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Physical Review

Quenching and Depolarization of Resonance Radiation by Collisions with Molecules of a Foreign Gas

A. Ellett, Leonard O. Olsen, Raymond Petersen

Published Jul 15, 1941• 8 citations
Publisher

Abstract

A semi-classical theory describing the quenching and depolarization of resonance radiation by collisions with foreign gas molecules is presented. The total depolarizing probability is divided into two parts to allow for adiabatic and nonadiabatic depolarization. The equations for polarization are generalized in order to apply to the case in which the observed polarization results from several lines belonging to a hyperfine group. The effect of a magnetic field applied along the direction of observation is also included in the treatment. Experimental results on the polarization of the $\ensuremath{\lambda}2537\mathrm{A}$ mercury line as a function of gas pressure and as a function of magnetic field at various fixed gas pressures show good agreement with the theory. Cross sections for quenching and depolarization have been calculated for the gases investigated and are presented in Table VI.

DOI
10.1103/physrev.60.107

Related papers

Quenching and Depolarization of Mercury Resonance Radiation by Nitrogen and Oxygen

Leonard O. Olsen, George P. Kerr

The quenching and depolarization of mercury resonance radiation by nitrogen and oxygen in the presence of a weak magnetic field are studied. These effects are proportional to gas pressure. The proportionality constants for each gas are determined. Results of tests on two samples of each gas are given, with generally good agreement between separate tests. Quenching and depolarizing cross sections are computed from the finally selected constants.The measurements here considered indicate that adiabatic depolarization, a phenomenon tentatively postulated in the theory, is not present in the case of nitrogen and oxygen.

Physical Review•Jul 15, 1947•7 citations

Depolarization of Resonance Radiation

Paul D. Foote

Depolarization and quenching of mercury resonance radiation are phenomena of quite different type. Depolarization is produced by two effects. With gases which quench by effecting the transition $^{3}P_{1}\ensuremath{\rightarrow}^{3}P_{0}$ upon collision with Hg\ensuremath{'} atoms, there exists a pronounced reverse transition $^{3}P_{0}\ensuremath{\rightarrow}^{3}P_{1}$ produced by collision with high speed molecules. Atoms which radiate without any collision emit polarized light under the conditions of the experiment. Those which become $^{3}P_{1}$ atoms after having existed as $^{3}P_{0}$ atoms have experienced a large number of collisions and have lost their orientation relative to the incident electric vector; accordingly they emit radiation polarized in random directions. The second depolarizing influence arises in collisions at distances exceeding the ordinary kinetic theory collision such as is described above, at which the distance is too great for a collision of the first or second type, but still small enough for the field of the gas atom to exert a perturbing influence on the orientation of the Hg\ensuremath{'} atom. Depolarization by ${\mathrm{H}}_{2}$ is an excellent example of the second influence while the first effect is sufficient to interpret the experimental data with the rare gases, the atomic fields of which decrease with a high power of the radial distance.

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Quenching and Depolarization of Mercury Resonance Radiation

J. S. Deech, John M. Pitre, L. Krause

The quenching and depolarization of mercury resonance radiation (2537 Å), induced in collisions of Hg(63P1) atoms with various molecules has been investigated using the method of delayed coincidences. The following total quenching cross sections have been obtained for the process Hg(63P1) → Hg(63P0, 61S0): Hg–H2, 24.6 Å2; Hg–D2, 22.7 Å2; Hg–CO, 21.7 Å2; Hg–CO2, 10.2 Å2; Hg–O2, 60.5 Å2; Hg–14N2, 0.73 Å2; Hg–15N2, 0.78 Å2; and Hg–Xe, < 0.002 Å2. A cross section of 267 Å2 has been measured for the depolarization of the resonance radiation by collisions with CO2 molecules.

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Depolarization of 6P322 cesium atoms, induced in collisions with noble gases

J. Guiry, L. Krause

Cross sections for relaxation of circular and linear polarization of $6^{2}P_{\frac{3}{2}}$ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-\AA{} Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ is coupled to the electronic angular momentum $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$, the measurements yielded depolarization cross sections $Q(\mathrm{circ}.)$ and $Q(\mathrm{lin}.)$, which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.

Physical Review A•Dec 1, 1976•13 citations

Disorientation of K(42P1/2) Atoms, Induced in Collisions with Noble Gases

B. Niewitecka, L. Krause

The cross sections for disorientation of 42P1/2 potassium atoms, induced in collisions with noble gas atoms, have been determined in zero magnetic field by studying the depolarization of K(7699 Å) resonance fluorescence in relation to noble gas pressures. Potassium vapor at low density, mixed with a noble gas in a fluorescence vessel, was irradiated with circularly polarized 7699 Å potassium resonance radiation and the resulting resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions and yielded the following disorientation cross sections which are appropriately corrected for the effect of nuclear spin: K–He, 24 ± 4 Å2; K–Ne, 21 ± 3 Å2; K–Ar, 37 ± 5 Å2; K–Kr, 51 ± 7 Å2; K–Xe, 69 ± 9 Å2. The cross sections are significantly smaller than values obtained previously in kilogauss fields.

Canadian Journal of Physics•Aug 1, 1975•13 citations

Hyperfine Structure and the Polarization of Mercury Resonance Radiation

Allan C. G. Mitchell

The general theory of the calculation of the polarization of resonance radiation is discussed for the case when hyperfine structure has to be considered. The polarization of mercury resonance radiation is computed for various orientations of electric vector and magnetic field, use being made of the hyperfine structure data of Sch\"uler and his collaborators. The polarization of the stepwise radiation of mercury is also calculated and the results compared with the experiments of Richter. Fair agreement between theory and experiment is found. von Keussler's method of calculating the polarization is discussed and it is shown that his method leads to incorrect results.

Physical Review•Jun 15, 1932•4 citations
A semi-classical theory describing the quenching and depolarization of resonance radiation by collisions with foreign gas molecules is presented. The total depolarizing probability is divided into two parts to allow for adiabatic and nonadiabatic depolarization. The equations for polarization are generalized in order to apply to the case in which the observed polarization results from several lines belonging to a hyperfine group. The effect of a magnetic field applied along the direction of observation is also included in the treatment. Experimental results on the polarization of the \ensuremathλ2537A\ensuremath{\lambda}2537\mathrm{A}\ensuremathλ2537A mercury line as a function of gas pressure and as a function of magnetic field at various fixed gas pressures show good agreement with the theory. Cross sections for quenching and depolarization have been calculated for the gases investigated and are presented in Table VI.
The quenching and depolarization of mercury resonance radiation by nitrogen and oxygen in the presence of a weak magnetic field are studied. These effects are proportional to gas pressure. The proportionality constants for each gas are determined. Results of tests on two samples of each gas are given, with generally good agreement between separate tests. Quenching and depolarizing cross sections are computed from the finally selected constants.The measurements here considered indicate that adiabatic depolarization, a phenomenon tentatively postulated in the theory, is not present in the case of nitrogen and oxygen.
Depolarization and quenching of mercury resonance radiation are phenomena of quite different type. Depolarization is produced by two effects. With gases which quench by effecting the transition $^{3}P_{1}\ensuremath{\rightarrow}^{3}P_{0}$ upon collision with Hg\ensuremath{'} atoms, there exists a pronounced reverse transition $^{3}P_{0}\ensuremath{\rightarrow}^{3}P_{1}$ produced by collision with high speed molecules. Atoms which radiate without any collision emit polarized light under the conditions of the experiment. Those which become 3P1^{3}P_{1}3P1​ atoms after having existed as 3P0^{3}P_{0}3P0​ atoms have experienced a large number of collisions and have lost their orientation relative to the incident electric vector; accordingly they emit radiation polarized in random directions. The second depolarizing influence arises in collisions at distances exceeding the ordinary kinetic theory collision such as is described above, at which the distance is too great for a collision of the first or second type, but still small enough for the field of the gas atom to exert a perturbing influence on the orientation of the Hg\ensuremath{'} atom. Depolarization by H2{\mathrm{H}}_{2}H2​ is an excellent example of the second influence while the first effect is sufficient to interpret the experimental data with the rare gases, the atomic fields of which decrease with a high power of the radial distance.
The quenching and depolarization of mercury resonance radiation (2537 Å), induced in collisions of Hg(63P1) atoms with various molecules has been investigated using the method of delayed coincidences. The following total quenching cross sections have been obtained for the process Hg(63P1) → Hg(63P0, 61S0): Hg–H2, 24.6 Å2; Hg–D2, 22.7 Å2; Hg–CO, 21.7 Å2; Hg–CO2, 10.2 Å2; Hg–O2, 60.5 Å2; Hg–14N2, 0.73 Å2; Hg–15N2, 0.78 Å2; and Hg–Xe, < 0.002 Å2. A cross section of 267 Å2 has been measured for the depolarization of the resonance radiation by collisions with CO2 molecules.
Cross sections for relaxation of circular and linear polarization of 62P326^{2}P_{\frac{3}{2}}62P23​​ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-\AA{} Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ is coupled to the electronic angular momentum $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$, the measurements yielded depolarization cross sections Q(circ.)Q(\mathrm{circ}.)Q(circ.) and Q(lin.)Q(\mathrm{lin}.)Q(lin.), which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.
The cross sections for disorientation of 42P1/2 potassium atoms, induced in collisions with noble gas atoms, have been determined in zero magnetic field by studying the depolarization of K(7699 Å) resonance fluorescence in relation to noble gas pressures. Potassium vapor at low density, mixed with a noble gas in a fluorescence vessel, was irradiated with circularly polarized 7699 Å potassium resonance radiation and the resulting resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions and yielded the following disorientation cross sections which are appropriately corrected for the effect of nuclear spin: K–He, 24 ± 4 Å2; K–Ne, 21 ± 3 Å2; K–Ar, 37 ± 5 Å2; K–Kr, 51 ± 7 Å2; K–Xe, 69 ± 9 Å2. The cross sections are significantly smaller than values obtained previously in kilogauss fields.
The general theory of the calculation of the polarization of resonance radiation is discussed for the case when hyperfine structure has to be considered. The polarization of mercury resonance radiation is computed for various orientations of electric vector and magnetic field, use being made of the hyperfine structure data of Sch\"uler and his collaborators. The polarization of the stepwise radiation of mercury is also calculated and the results compared with the experiments of Richter. Fair agreement between theory and experiment is found. von Keussler's method of calculating the polarization is discussed and it is shown that his method leads to incorrect results.