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Physical Review A

Cross-section measurement for the energy-transfer collisions Na(3P)+Na(3P)→Na(5S,4D)+Na(3S)

M. Allegrini, Paola Bicchi, L. Moi

Published Sep 1, 1983• 59 citations
Publisher

Abstract

We report our measurements of the cross sections ${\ensuremath{\sigma}}_{5S}$ and ${\ensuremath{\sigma}}_{4D}$ for the electronic-energy-transfer process $\mathrm{Na}(3P)+\mathrm{Na}(3P)\ensuremath{\rightarrow}\mathrm{Na}(5S,4D)+\mathrm{Na}(3S)$. To obtain these cross sections we have measured the fluorescence intensity for the transitions $5S\ensuremath{\rightarrow}3P$, $4D\ensuremath{\rightarrow}3P$, and $3P\ensuremath{\rightarrow}3S$ in sodium vapor excited with a cw dye laser. The study of this electronic energy transfer is complicated and there is a large disagreement (\ensuremath{\gtrsim}${10}^{4}$) among reported measurements. We believe we have avoided most of the difficulties of previous experiments. Our results are ${\ensuremath{\sigma}}_{5S}=(2.0\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{2}$ and ${\ensuremath{\sigma}}_{4D}=(3.2\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ ${\mathrm{cm}}^{\ensuremath{-}2}$, and they are compared with the results of other experiments.

DOI
10.1103/physreva.28.1338

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Abstract. The cross sections for the Na.4D/! Na.4F / excitation energy transfer induced by collisions with He, Ar and Na ground-state atoms have been measured. The sodium atoms in the 4D state have been produced by two-photon excitation using cw laser radiation at 578.89 nm. Within a model which takes into account collisional population and depopulation of the 4F level as well as radiative relaxation (direct or cascade) of the 3D, 4P, 4D and 4F states ending in the 3P level, the rate for the Na.4D / ! Na.4F / collisional transfer turns out to be related to the ratio of the steady-state populations created in 3D and 4D states. They have been determined by measuring the fluorescence intensities of the 3D! 3P and 4D! 3P transitions. The measurements yield the following cross section values for those

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Cross sections for the excitation energy transfer induced by collisions with He, Ar and Na atoms

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Sodium 3P fine-structure excitation transfer induced by collisions with rubidium and caesium atoms

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The cross sections for the excitation energy transfer in the collisional processes Na*(3P 1 2/)+M(nS 1 2/) to or from Na*(3p 3 2/)+m(Ns 3 2/), m being ground-state Rb (n=5) or Cs (n=6) atom, have been measured by laser fluorescence method. With either of the two sodium 3P fine-structure states optically excited, the intensity ratio of the sensitized to direct fluorescence was measured. The polarization effects due to partially polarized and anisotropic direct fluorescence were investigated. The measured cross sections (T=530 K) for the sodium 3P fine-structure excitation transfer induced by collisions with Rb are: sigma ( 1 / 2 to 3 / 2 )=170 AA 2 , with an overall accuracy of 20%. The corresponding values in the Cs case are: sigma ( 1 / 2 to 3 / 2 )=140 AA 2 , sigma ( 3 / 2 to 1 / 2 )=83 AA 2 . The theoretical calculations reveal the decisive role of the dipole-quadrupole interaction. The obtained values are in satisfactory agreement with the experiment only if both the dipole-dipole and dipole-quadrupole interactions are taken into account, while the calculations involving the dipole-dipole term alone yield the cross section values which are as much as one order of magnitude lower than the experimentally observed ones.

Journal of Physics B Atomic Molecular and Optical Physics•Oct 14, 1994•4 citations
We report our measurements of the cross sections \ensuremathσ5S{\ensuremath{\sigma}}_{5S}\ensuremathσ5S​ and \ensuremathσ4D{\ensuremath{\sigma}}_{4D}\ensuremathσ4D​ for the electronic-energy-transfer process Na(3P)+Na(3P)\ensuremath→Na(5S,4D)+Na(3S)\mathrm{Na}(3P)+\mathrm{Na}(3P)\ensuremath{\rightarrow}\mathrm{Na}(5S,4D)+\mathrm{Na}(3S)Na(3P)+Na(3P)\ensuremath→Na(5S,4D)+Na(3S). To obtain these cross sections we have measured the fluorescence intensity for the transitions 5S\ensuremath→3P5S\ensuremath{\rightarrow}3P5S\ensuremath→3P, 4D\ensuremath→3P4D\ensuremath{\rightarrow}3P4D\ensuremath→3P, and 3P\ensuremath→3S3P\ensuremath{\rightarrow}3S3P\ensuremath→3S in sodium vapor excited with a cw dye laser. The study of this electronic energy transfer is complicated and there is a large disagreement (\ensuremath{\gtrsim}104{10}^{4}104) among reported measurements. We believe we have avoided most of the difficulties of previous experiments. Our results are \ensuremathσ5S=(2.0\ifmmode±\else\textpm\fi0.7)\ifmmode×\else\texttimes\fi10\ensuremath−15{\ensuremath{\sigma}}_{5S}=(2.0\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\ensuremathσ5S​=(2.0\ifmmode±\else\textpm\fi0.7)\ifmmode×\else\texttimes\fi10\ensuremath−15 cm2{\mathrm{cm}}^{2}cm2 and \ensuremathσ4D=(3.2\ifmmode±\else\textpm\fi1.1)\ifmmode×\else\texttimes\fi10\ensuremath−15{\ensuremath{\sigma}}_{4D}=(3.2\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}\ensuremathσ4D​=(3.2\ifmmode±\else\textpm\fi1.1)\ifmmode×\else\texttimes\fi10\ensuremath−15 cm\ensuremath−2{\mathrm{cm}}^{\ensuremath{-}2}cm\ensuremath−2, and they are compared with the results of other experiments.
We measured the cross section for the collision transfer process Na(4D)+Na (3S)Na(4F)+Na(3S). The 4D state was excited by two photon absorption using a tunable dye laser. Since the direct 4F→3D fluorescence can not be detected with our apparatus, we monitored instead the cascade 3D→3P and 4D→3P fluorescence. Relative intensity of the fluorescence, combined with the measurement of sodium density, yielded cross section σ_(4D)→(4F)=1.3×10~(-14)±28％(cm~2). Our result is compared to other experiments.
We report the measurements of the temperature dependence of the cross section 4D for the energy pooling process Na(3P)+Na(3P) Na(4D)+Na(3S). The latest two, as yet undisputed, results for 4D obtained by different authors at T = 597 K and T = 483 K suggest that this cross section decreases with increasing T , which contradicts the theory and other experiments on similar processes. To resolve this controversy and to examine the temperature trend of the cross section, we have measured the 4D in the temperature range 567-705 K, covering the high-temperature region that has not yet been investigated experimentally. To determine 4D we have excited sodium atoms in the quasistatic wing of the D1 line using a cw dye laser and measured the fluorescence intensity for the 4D 3P 3/2 transition, relative to the intensity of the optically thin quasistatic wing of the D2 line. The spatial distribution of the number density of the sodium atoms in the 3P 3/2 state and the sodium ground-state number density were measured too. The method used for the determination of the cross section is advantageous since it entirely circumvents the need to account for the radiation trapping of 3P level radiation, which was substantial under experimental conditions of the ground-state densities being 10 14 -10 16 cm -3 . The measurements of the cross section 4D in the investigated temperature range have shown that it increases as ~exp(- E / kT ). From the experiment we obtained E = (608±95) cm -1 , which is in excellent agreement with the energy defect (613 cm -1 ) for the considered process, and in fair agreement with the values which follow from recent theoretical calculations.
Abstract. The cross sections for the Na.4D/! Na.4F / excitation energy transfer induced by collisions with He, Ar and Na ground-state atoms have been measured. The sodium atoms in the 4D state have been produced by two-photon excitation using cw laser radiation at 578.89 nm. Within a model which takes into account collisional population and depopulation of the 4F level as well as radiative relaxation (direct or cascade) of the 3D, 4P, 4D and 4F states ending in the 3P level, the rate for the Na.4D / ! Na.4F / collisional transfer turns out to be related to the ratio of the steady-state populations created in 3D and 4D states. They have been determined by measuring the fluorescence intensities of the 3D! 3P and 4D! 3P transitions. The measurements yield the following cross section values for those
Cross section σ4D→4F was measured for the collision transfer process of Na(4D) +Na(3S)→Na(4F)+Na(3S).The 4D state is excited by two-photon absorption using a tunable dye laser.Since the 4F→3D fluorescence can not be detected directly with the apparatus used the cascade 3D→3P fluorescence is monitored instead.Then the cross-section σ4D→4F=(1.3±0.3)×10^-14cm^2 is got from the relative intensity of the fluorescence.A theoretical evaluation of σ4D→4F is also given and compared with experimental results.
The cross sections for the excitation energy transfer induced by collisions with He, Ar and Na ground-state atoms have been measured. The sodium atoms in the 4D state have been produced by two-photon excitation using cw laser radiation at 578.89 nm. Within a model which takes into account collisional population and depopulation of the 4F level as well as radiative relaxation (direct or cascade) of the 3D, 4P, 4D and 4F states ending in the 3P level, the rate for the collisional transfer turns out to be related to the ratio of the steady-state populations created in 3D and 4D states. They have been determined by measuring the fluorescence intensities of the and transitions. The measurements yield the following cross section values for those processes investigated: , and , at .
The cross sections for the excitation energy transfer in the collisional processes Na*(3P 1 2/)+M(nS 1 2/) to or from Na*(3p 3 2/)+m(Ns 3 2/), m being ground-state Rb (n=5) or Cs (n=6) atom, have been measured by laser fluorescence method. With either of the two sodium 3P fine-structure states optically excited, the intensity ratio of the sensitized to direct fluorescence was measured. The polarization effects due to partially polarized and anisotropic direct fluorescence were investigated. The measured cross sections (T=530 K) for the sodium 3P fine-structure excitation transfer induced by collisions with Rb are: sigma ( 1 / 2 to 3 / 2 )=170 AA 2 , with an overall accuracy of 20%. The corresponding values in the Cs case are: sigma ( 1 / 2 to 3 / 2 )=140 AA 2 , sigma ( 3 / 2 to 1 / 2 )=83 AA 2 . The theoretical calculations reveal the decisive role of the dipole-quadrupole interaction. The obtained values are in satisfactory agreement with the experiment only if both the dipole-dipole and dipole-quadrupole interactions are taken into account, while the calculations involving the dipole-dipole term alone yield the cross section values which are as much as one order of magnitude lower than the experimentally observed ones.