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Physical Review A

Excitation transfer among, and quenching of, the barium 6s5d 3 DJ metastable levels due to collisions with argon, nitrogen, and barium perturbers

E. Ehrlacher, John Huennekens

Published Dec 1, 1994• 26 citations
Publisher

Abstract

We describe a set of experiments that investigate excitation transfer among the barium 6s5d $^{3}$${\mathit{D}}_{\mathit{J}}$ metastable levels due to collisions with argon perturber atoms, and quenching of atoms in these levels by nitrogen perturber molecules. The metastable levels were populated through optical pumping of the 6${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$\ensuremath{\rightarrow}6s6p $^{3}$${\mathit{P}}_{1}^{\mathit{o}}$ intercombination transition with a pulsed laser, followed by stimulated emission or stimulated Raman scattering into the 6s5d $^{3}$${\mathit{D}}_{1,2}$ levels. Collisional mixing then distributed population throughout the $^{3}$${\mathit{D}}_{\mathit{J}}$ levels. Time-dependent absorption coefficients were obtained by measuring the transmission of a weak cw probe laser beam (after the pulsed laser fired) at several perturber number densities. Argon buffer gas was used to investigate fine-structure mixing, and nitrogen was used to study quenching. The time-dependent absorption coefficients were fitted to appropriate fitting functions, obtained by solving the set of coupled rate equations used to model the time evolution of the metastable level populations. The buildup rates of the initially unpopulated $^{3}$${\mathit{D}}_{3}$ and underpopulated $^{3}$${\mathit{D}}_{1}$ levels were used to determine the collisional mixing rates, while the measured decay rates of the $^{3}$${\mathit{D}}_{\mathit{J}}$ level populations yielded the quenching rates. From plots of buildup rates versus argon number density for the $^{3}$${\mathit{D}}_{1,3}$ states, we were able to determine four of the six fine-structure mixing rate coefficients ${\mathit{k}}_{\mathit{i}\mathit{j}}$.The results are ${\mathit{k}}_{12}$=(1.71\ifmmode\pm\else\textpm\fi{}0.18), ${\mathit{k}}_{21}$=(1.39\ifmmode\pm\else\textpm\fi{}0.13), ${\mathit{k}}_{23}$=(1.42\ifmmode\pm\else\textpm\fi{}0.13), and ${\mathit{k}}_{32}$=(1.92\ifmmode\pm\else\textpm\fi{}0.16)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The experiment is not sensitive to the values of ${\mathit{k}}_{13}$ and ${\mathit{k}}_{31}$. Estimated rate coefficients for excitation transfer among the $^{3}$${\mathit{D}}_{\mathit{J}}$ levels due to collisions with barium atoms are ${\mathit{k}}_{21}^{\mathrm{Ba}}$=1.3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ and ${\mathit{k}}_{23}^{\mathrm{Ba}}$=5.8\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. A plot of the population decay rates versus ${\mathrm{N}}_{2}$ number density for each of the three metastable levels yielded the average nitrogen quenching rate coefficient ${\mathit{k}}_{\mathit{q}}$=(3.14\ifmmode\pm\else\textpm\fi{}0.19)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$ ${\mathrm{cm}}^{3}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$.

DOI
10.1103/physreva.50.4786

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We describe a set of experiments that investigate diffusion of barium 6s5d${\mathrm{}}^{3}$${\mathit{D}}_{\mathit{J}}$ metastable level and 6${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$ ground-state atoms through the noble gases: He, Ne, Ar, Kr, and Xe. The barium metastable levels were populated through optical pumping of the 6${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$\ensuremath{\rightarrow}6s6p${\mathrm{}}^{3}$${\mathit{P}}_{1}^{\mathit{o}}$ intercombination transition with a pulsed laser, followed by spontaneous or stimulated emission into the 6s5d${\mathrm{}}^{3}$${\mathit{D}}_{1,2}$ levels. Collisional mixing then distributed population throughout the 6s5d${\mathrm{}}^{3}$${\mathit{D}}_{\mathit{J}}$ levels. A weak narrow-band cw laser was tuned to appropriate transitions to probe the spatial distribution of metastable level atoms, as well as the hole created in the ground-state spatial distribution, by the pulsed laser. Time-dependent absorption coefficients were obtained by measuring the transmission of the probe laser at several different pump-probe spatial separations. From these absorption data, spatial number density profiles were mapped out for various times following the firing of the pump laser. These density profiles were used to determine the diffusion coefficient for each state at a particular buffer-gas pressure and temperature. From these pressure- and temperature-dependent diffusion coefficients D, we determined the thermally averaged diffusion cross sections ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6s5d${\mathrm{}}^{3}$${\mathit{D}}_{\mathit{J}}$) and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$) for the metastable and ground-state atoms diffusing through the noble gases, respectively. We also report values for the scaled standard diffusion coefficients ${\mathit{D}}_{0}$. Our experimental values of the thermally averaged diffusion cross sections ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6s5d${\mathrm{}}^{3}$${\mathit{D}}_{\mathit{J}}$) and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$) for the barium-helium system are compared with values calculated from published, theoretical barium-helium potentials and the agreement is excellent. \textcopyright{} 1996 The American Physical Society.

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J. Brust, Alan C. Gallagher

We present a time resolved study of excitation transfer processes between the low lying excited states of barium (6s6p $^{3}$${\mathit{P}}_{\mathit{J}}$, 6s5d $^{1}$${\mathit{D}}_{2}$, 6s5d $^{3}$${\mathit{D}}_{\mathit{J}}$) induced by collisions with noble gases. The transient excited state populations have been measured by means of fluorescence and absorption spectroscopy. Cross sections for spin-changing collisions from $^{3}$${\mathit{P}}_{1}$ to $^{1}$${\mathit{D}}_{2}$ and from $^{1}$${\mathit{D}}_{2}$ to $^{3}$${\mathit{D}}_{3}$ as well as for fine-structure mixing within the $^{3}$D multiplet were obtained by fitting the numerical solution of a seven-state system of rate equations including diffusion to the experimental data. We compare our results to experimental findings for other alkaline earth metals and report an improved value of the lifetime of the 6s6p $^{3}$${\mathit{P}}_{1}$ state of barium.

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Radiative lifetimes, collisional mixing, and quenching of the cesium 5DJ levels

Antonio Sasso, Wolfgang Demtröder, T. Colbert +3 more

We report the results of a series of pulsed and cw laser experiments which measure spontaneous and effective lifetimes of the Cs(5DJ) levels and investigate excitation-transfer collisions involving Cs(5DJ) atoms and ground-state-cesium perturbers. With cw excitation of the dipole-forbidden but electric-quadrupole-allowed 6S1/2\ensuremath{\rightarrow}5D5/2 transition, we monitor the ratio of sensitized to direct fluorescence, i.e., I5D3/2\ensuremath{\rightarrow}6P1/2/I5D5/2\ensuremath{\rightarrow}6P3/2. A rate-equation analysis of these data yields values for the Cs(5D5/2)+Cs(6S)\ensuremath{\rightarrow}Cs(5D3/2)+Cs(6S) excitation-transfer rate, and for the rate of quenching of Cs(5D) by ground-state perturbers. The role of out-of-multiplet quenching is discussed at length, and we have demonstrated that quenching by ground-state atoms dominates over that by cesium dimers under these conditions. In the pulsed-laser experiments, the temporal evolution of the 5DJ\ensuremath{\rightarrow}6S and cascade 6PJ\ensuremath{'}\ensuremath{\rightarrow}6S fluorescence was observed following either direct forbidden-line pumping of one fine-structure level, or indirect excitation of both fine-structure levels (i.e., molecular excitation followed by predissociation). Analysis of the buildup and decay rates of the various levels as a function of cesium density yields values for the natural lifetimes of the Cs(5DJ) levels, as well as for the excitation transfer and quenching rates. Best values for the lifetimes and cross sections for Cs-Cs collisions obtained from these combined experiments are \ensuremath{\tau}5D=1250\ifmmode\pm\else\textpm\fi{}115 ns, \ensuremath{\sigma}5/2\ensuremath{\rightarrow}3/2=36\ifmmode\pm\else\textpm\fi{}8 \AA{}2, and \ensuremath{\sigma}5D=30\ifmmode\pm\else\textpm\fi{}3 \AA{}2. In addition, numbers for the 6P level-quenching cross sections due to collisions with Cs atoms and Cs2 molecules, respectively, were obtained: \ensuremath{\sigma}6P(Cs)=6.6\ifmmode\pm\else\textpm\fi{}3.0 \AA{}2 and \ensuremath{\sigma}6P(Cs2)=863\ifmmode\pm\else\textpm\fi{}260 \AA{}2. In the discussion, we show how these new values can be used to reconcile the seemingly discrepant results of several previous studies.

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Time-resolved fluorescence and population measurements in laser-pumped barium vapour

J. LEONARD BOWEN, Anne P. Thorne

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Collisional transfer between the 6s′[12]0,1 and 6p[12]1 xenon levels

N. Sadeghi, J. Sabbagh

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Physical Review A•Dec 1, 1977•56 citations
We describe a set of experiments that investigate excitation transfer among the barium 6s5d ^{3}$${\mathit{D}}_{\mathit{J}} metastable levels due to collisions with argon perturber atoms, and quenching of atoms in these levels by nitrogen perturber molecules. The metastable levels were populated through optical pumping of the 6s2{\mathit{s}}^{2}s2 ^{1}$${\mathit{S}}_{0}\ensuremath{\rightarrow}6s6p ^{3}$${\mathit{P}}_{1}^{\mathit{o}} intercombination transition with a pulsed laser, followed by stimulated emission or stimulated Raman scattering into the 6s5d ^{3}$${\mathit{D}}_{1,2} levels. Collisional mixing then distributed population throughout the ^{3}$${\mathit{D}}_{\mathit{J}} levels. Time-dependent absorption coefficients were obtained by measuring the transmission of a weak cw probe laser beam (after the pulsed laser fired) at several perturber number densities. Argon buffer gas was used to investigate fine-structure mixing, and nitrogen was used to study quenching. The time-dependent absorption coefficients were fitted to appropriate fitting functions, obtained by solving the set of coupled rate equations used to model the time evolution of the metastable level populations. The buildup rates of the initially unpopulated ^{3}$${\mathit{D}}_{3} and underpopulated ^{3}$${\mathit{D}}_{1} levels were used to determine the collisional mixing rates, while the measured decay rates of the ^{3}$${\mathit{D}}_{\mathit{J}} level populations yielded the quenching rates. From plots of buildup rates versus argon number density for the ^{3}$${\mathit{D}}_{1,3} states, we were able to determine four of the six fine-structure mixing rate coefficients kij{\mathit{k}}_{\mathit{i}\mathit{j}}kij​.The results are k12{\mathit{k}}_{12}k12​=(1.71\ifmmode\pm\else\textpm\fi{}0.18), k21{\mathit{k}}_{21}k21​=(1.39\ifmmode\pm\else\textpm\fi{}0.13), k23{\mathit{k}}_{23}k23​=(1.42\ifmmode\pm\else\textpm\fi{}0.13), and k32{\mathit{k}}_{32}k32​=(1.92\ifmmode\pm\else\textpm\fi{}0.16)\ifmmode\times\else\texttimes\fi{}10\ensuremath−13{10}^{\mathrm{\ensuremath{-}}13}10\ensuremath−13 cm3{\mathrm{cm}}^{3}cm3 s\ensuremath−1{\mathrm{s}}^{\mathrm{\ensuremath{-}}1}s\ensuremath−1. The experiment is not sensitive to the values of k13{\mathit{k}}_{13}k13​ and k31{\mathit{k}}_{31}k31​. Estimated rate coefficients for excitation transfer among the ^{3}$${\mathit{D}}_{\mathit{J}} levels due to collisions with barium atoms are k21Ba{\mathit{k}}_{21}^{\mathrm{Ba}}k21Ba​=1.3\ifmmode\times\else\texttimes\fi{}10\ensuremath−10{10}^{\mathrm{\ensuremath{-}}10}10\ensuremath−10 cm3{\mathrm{cm}}^{3}cm3 s\ensuremath−1{\mathrm{s}}^{\mathrm{\ensuremath{-}}1}s\ensuremath−1 and k23Ba{\mathit{k}}_{23}^{\mathrm{Ba}}k23Ba​=5.8\ifmmode\times\else\texttimes\fi{}10\ensuremath−10{10}^{\mathrm{\ensuremath{-}}10}10\ensuremath−10 cm3{\mathrm{cm}}^{3}cm3 s\ensuremath−1{\mathrm{s}}^{\mathrm{\ensuremath{-}}1}s\ensuremath−1. A plot of the population decay rates versus N2{\mathrm{N}}_{2}N2​ number density for each of the three metastable levels yielded the average nitrogen quenching rate coefficient kq{\mathit{k}}_{\mathit{q}}kq​=(3.14\ifmmode\pm\else\textpm\fi{}0.19)\ifmmode\times\else\texttimes\fi{}10\ensuremath−11{10}^{\mathrm{\ensuremath{-}}11}10\ensuremath−11 cm3{\mathrm{cm}}^{3}cm3 s\ensuremath−1{\mathrm{s}}^{\mathrm{\ensuremath{-}}1}s\ensuremath−1.
We describe a set of experiments that investigate diffusion of barium 6s5d3{\mathrm{}}^{3}3DJ{\mathit{D}}_{\mathit{J}}DJ​ metastable level and 6s2{\mathit{s}}^{2}s21{\mathrm{}}^{1}1S0{\mathit{S}}_{0}S0​ ground-state atoms through the noble gases: He, Ne, Ar, Kr, and Xe. The barium metastable levels were populated through optical pumping of the 6s2{\mathit{s}}^{2}s21{\mathrm{}}^{1}1S0{\mathit{S}}_{0}S0​\ensuremath{\rightarrow}6s6p3{\mathrm{}}^{3}3P1o{\mathit{P}}_{1}^{\mathit{o}}P1o​ intercombination transition with a pulsed laser, followed by spontaneous or stimulated emission into the 6s5d3{\mathrm{}}^{3}3D1,2{\mathit{D}}_{1,2}D1,2​ levels. Collisional mixing then distributed population throughout the 6s5d3{\mathrm{}}^{3}3DJ{\mathit{D}}_{\mathit{J}}DJ​ levels. A weak narrow-band cw laser was tuned to appropriate transitions to probe the spatial distribution of metastable level atoms, as well as the hole created in the ground-state spatial distribution, by the pulsed laser. Time-dependent absorption coefficients were obtained by measuring the transmission of the probe laser at several different pump-probe spatial separations. From these absorption data, spatial number density profiles were mapped out for various times following the firing of the pump laser. These density profiles were used to determine the diffusion coefficient for each state at a particular buffer-gas pressure and temperature. From these pressure- and temperature-dependent diffusion coefficients D, we determined the thermally averaged diffusion cross sections ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6s5d3{\mathrm{}}^{3}3DJ{\mathit{D}}_{\mathit{J}}DJ​) and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6s2{\mathit{s}}^{2}s21{\mathrm{}}^{1}1S0{\mathit{S}}_{0}S0​) for the metastable and ground-state atoms diffusing through the noble gases, respectively. We also report values for the scaled standard diffusion coefficients D0{\mathit{D}}_{0}D0​. Our experimental values of the thermally averaged diffusion cross sections ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6s5d3{\mathrm{}}^{3}3DJ{\mathit{D}}_{\mathit{J}}DJ​) and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{D}}$(6s2{\mathit{s}}^{2}s21{\mathrm{}}^{1}1S0{\mathit{S}}_{0}S0​) for the barium-helium system are compared with values calculated from published, theoretical barium-helium potentials and the agreement is excellent. \textcopyright{} 1996 The American Physical Society.
We present a time resolved study of excitation transfer processes between the low lying excited states of barium (6s6p 3^{3}3PJ{\mathit{P}}_{\mathit{J}}PJ​, 6s5d 1^{1}1D2{\mathit{D}}_{2}D2​, 6s5d 3^{3}3DJ{\mathit{D}}_{\mathit{J}}DJ​) induced by collisions with noble gases. The transient excited state populations have been measured by means of fluorescence and absorption spectroscopy. Cross sections for spin-changing collisions from 3^{3}3P1{\mathit{P}}_{1}P1​ to 1^{1}1D2{\mathit{D}}_{2}D2​ and from 1^{1}1D2{\mathit{D}}_{2}D2​ to 3^{3}3D3{\mathit{D}}_{3}D3​ as well as for fine-structure mixing within the 3^{3}3D multiplet were obtained by fitting the numerical solution of a seven-state system of rate equations including diffusion to the experimental data. We compare our results to experimental findings for other alkaline earth metals and report an improved value of the lifetime of the 6s6p 3^{3}3P1{\mathit{P}}_{1}P1​ state of barium.
Rate coefficients for energy-pooling collisions between low-lying excited states of Ba have been measured. The 6s6p(3{(}^{3}(3P1{\mathit{P}}_{1}P1​) level in Ba is pumped by a cw diode laser, and radiative decay and collisions with buffer-gas atoms also populate the 5d6s(1{(}^{1}(1D) and 5d6s(3{(}^{3}(3D) metastable levels. The densities of these low-lying excited states are measured by the absorption of lines from a Ba hollow-cathode lamp, and the states populated by energy-pooling collisions are studied by comparing their fluorescence intensity to that of the laser-excited level. The rate coefficients are on the order of gas-kinetic rates, and they are not strongly dependent on energy defect, spin changes, or angular-momentum changes.
We report the results of a series of pulsed and cw laser experiments which measure spontaneous and effective lifetimes of the Cs(5DJ) levels and investigate excitation-transfer collisions involving Cs(5DJ) atoms and ground-state-cesium perturbers. With cw excitation of the dipole-forbidden but electric-quadrupole-allowed 6S1/2\ensuremath{\rightarrow}5D5/2 transition, we monitor the ratio of sensitized to direct fluorescence, i.e., I5D3/2\ensuremath{\rightarrow}6P1/2/I5D5/2\ensuremath{\rightarrow}6P3/2. A rate-equation analysis of these data yields values for the Cs(5D5/2)+Cs(6S)\ensuremath{\rightarrow}Cs(5D3/2)+Cs(6S) excitation-transfer rate, and for the rate of quenching of Cs(5D) by ground-state perturbers. The role of out-of-multiplet quenching is discussed at length, and we have demonstrated that quenching by ground-state atoms dominates over that by cesium dimers under these conditions. In the pulsed-laser experiments, the temporal evolution of the 5DJ\ensuremath{\rightarrow}6S and cascade 6PJ\ensuremath{'}\ensuremath{\rightarrow}6S fluorescence was observed following either direct forbidden-line pumping of one fine-structure level, or indirect excitation of both fine-structure levels (i.e., molecular excitation followed by predissociation). Analysis of the buildup and decay rates of the various levels as a function of cesium density yields values for the natural lifetimes of the Cs(5DJ) levels, as well as for the excitation transfer and quenching rates. Best values for the lifetimes and cross sections for Cs-Cs collisions obtained from these combined experiments are \ensuremath{\tau}5D=1250\ifmmode\pm\else\textpm\fi{}115 ns, \ensuremath{\sigma}5/2\ensuremath{\rightarrow}3/2=36\ifmmode\pm\else\textpm\fi{}8 \AA{}2, and \ensuremath{\sigma}5D=30\ifmmode\pm\else\textpm\fi{}3 \AA{}2. In addition, numbers for the 6P level-quenching cross sections due to collisions with Cs atoms and Cs2 molecules, respectively, were obtained: \ensuremath{\sigma}6P(Cs)=6.6\ifmmode\pm\else\textpm\fi{}3.0 \AA{}2 and \ensuremath{\sigma}6P(Cs2)=863\ifmmode\pm\else\textpm\fi{}260 \AA{}2. In the discussion, we show how these new values can be used to reconcile the seemingly discrepant results of several previous studies.
Time-resolved measurements of fluorescence and level populations have been made on barium vapour illuminated by an intense pulse of laser radiation (1 MW cm -2 , 50 ns FWHM) tuned to the resonance transition of Ba I, 6s 2 1 S 0 -6s6p 1 P 1 , at 5535 AA. Barium number densities between 10 13 -10 15 cm -3 were investigated, using a buffer gas of helium at 100 Torr. Fluorescence was measured with two different geometrical arrangements, one allowing partial spatial resolution. In neither case did the observed fluorescence saturate with increasing laser power, although the maximum flux was more than sufficient to burn through the vapour column, as confirmed by transmission measurements. The power loss from the laser beam was found to be compatible with the scattered radiation from the pumped column in the absence of radiation trapping. In contrast to other similar experiments, no significant ionisation was detected (<5%). Time-resolved population measurements by anomalous dispersion on the 6s6p 3 P 2 and 6s5d 1 D 2 metastable levels yielded quenching cross sections for both Ba-Ba and Ba-He collisions, but gave anomalous result for the peak populations. A qualitative explanation of the fluorescence anomaly is proposed on the basis of the AC Stark effect, and it is shown that the same effect can inhibit the onset of stimulated emission to the metastable D levels.
The destruction rates of the xenon $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{0}$ metastable and $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{1}$ resonance atoms by collisions with ground-state xenon atoms have been measured by studying the temporal dependence of the number densities of the $6{s}^{\ensuremath{'}}$ and 6p6p6p atoms. The studies have been made both during the earlier afterglow of a xenon pulsed discharge and after the selective production of the $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{0,1}$ atoms by a laser excitation in the late afterglow. An original optical pumping technique, using a tunable pulsed dye laser, was employed to populate the $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{0,1}$ levels by excitation of the 6s[32]26s{[\frac{3}{2}]}_{2}6s[23​]2​ long-lived metastable atoms to $6{p}^{\ensuremath{'}}$ levels. The pressure dependence of the decay frequencies of these $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{0,1}$ atoms was analyzed in the xenon pressure range of 0.04 to 1 torr and a kinetic model describing the evolution of the densities of these atoms after their production was established. The rate coefficients for the relaxation of the $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{0}$ metastable and $6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{1}$ resonance atoms by two-body collisions involving a ground-state xenon atom are (8.45\ifmmode\pm\else\textpm\fi{}0.85) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}12}$ cm3{\mathrm{cm}}^{3}cm3 ${\mathrm{sec}}^{\ensuremath{-}1}$ and (6.65 \ifmmode\pm\else\textpm\fi{} 1.00) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}11}$ cm3{\mathrm{cm}}^{3}cm3 ${\mathrm{sec}}^{\ensuremath{-}1}$, respectively. Results show that, in fact, at least 75% of this relaxation is a transfer of population to the 6p[12]16p{[\frac{1}{2}]}_{1}6p[21​]1​ level following ${\mathrm{Xe}}^{*}(6{s}^{\ensuremath{'}}{[\frac{1}{2}]}_{0,1})+\mathrm{Xe}\ensuremath{\rightleftarrows}{\mathrm{Xe}}^{*}(6p{[\frac{1}{2}]}_{1})+\mathrm{Xe}\ensuremath{-}\ensuremath{\Delta}E$. These collisional transfer processes have been explained by means of Mulliken's xenon molecular potential curves.