Journal of Physics B Atomic Molecular and Optical Physics

Polarization dependence of energy pooling reactions between two Na* (3p) atoms

J H Nijland, J. A. de Gouw, Cornelis J. G. J. Uiterwaal, H.A. Dijkerman, H G M Heideman

Published Sep 28, 1990• 9 citations

Abstract

The authors have studied in a beam experiment the energy pooling reaction between two laser-excited Na* (3p) atoms, where in the final state one Na atom is in the 5s or 4d state and the other in the ground state. They have found that this reaction is strongly dependent on the polarization of the laser light used to prepare the Na*(3p) atoms. An analysis of theoretical potential curves suggests that the reaction mainly proceeds via the input channel where one of the atoms is in the M=0 and the other in the M=1 substate. Their experimental results are in qualitative agreement with that suggestion.

DOI: 10.1088/0953-4075/23/18/007

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Journal of Physics B Atomic Molecular and Optical Physics

Polarization dependence of energy pooling reactions between two Na* (3p) atoms

J H Nijland, J. A. de Gouw, Cornelis J. G. J. Uiterwaal, H.A. Dijkerman, H G M Heideman

Published Sep 28, 1990• 9 citations

Publisher

Abstract

DOI: 10.1088/0953-4075/23/18/007

Related papers

Cross sections and coherences for energy pooling reactions between two Na*(3p) atoms

J H Nijland, J. A. de Gouw, H.A. Dijkerman +1 more

The authors have studied, in a beam experiment, the energy pooling reaction between two laser excited Na*(3p) atoms, where in the final state one of the Na atoms is in the 5s or 4d state and the other in the ground state. The polarization of the Na*(3p) atoms can be varied by changing the laser polarization. By using two counterpropagating Na beams and intersecting them twice by a laser beam (directly and indirectly after reflection against a mirror) the polarization of the two collision partners can be varied independently. Since the laser beam intersects the Na beams at an angle of 87.6 degrees , the relative velocity of the atoms can furthermore be selected by exploiting the Doppler effect. In the authors' experiment the relevant cross sections and coherences, specified according to the various magnetic substate combinations of the colliding Na*(3p) atoms, can be determined.The authors have studied, in a beam experiment, the energy pooling reaction between two laser excited Na*(3p) atoms, where in the final state one of the Na atoms is in the 5s or 4d state and the other in the ground state. The polarization of the Na*(3p) atoms can be varied by changing the laser polarization. By using two counterpropagating Na beams and intersecting them twice by a laser beam (directly and indirectly after reflection against a mirror) the polarization of the two collision partners can be varied independently. Since the laser beam intersects the Na beams at an angle of 87.6 degrees , the relative velocity of the atoms can furthermore be selected by exploiting the Doppler effect. In the authors' experiment the relevant cross sections and coherences, specified according to the various magnetic substate combinations of the colliding Na*(3p) atoms, can be determined.

Journal of Physics B Atomic Molecular and Optical PhysicsJun 28, 199219 citations

Energy pooling reactions between two Na* (3p) atoms specified according to magnetic substate combinations

J H Nijland, Jan Jette Blange, H. Rudolph +2 more

In a beam experiment the authors have studied the energy pooling reaction between two laser excited Na* (3p) atoms, where in the final state one of the sodium atoms is in the 5s or 4d state and the other in the ground state. They have determined all eight independent partial cross sections and coherence terms, specified according to the various magnetic substate combinations of the colliding Na* (3p) atoms, as a function of the collision velocity. This is the maximum information that can be extracted from the experiment given the symmetry of the detection scheme. By applying a weak magnetic field, to orient the Na* (3p) atoms, the authors were able to distinguish between the two partial cross sections sigma 11 and sigma 1-1 , where the subscripts 11 and 1-1 refer to the initial magnetic substate combinations of the two collision partners. By using an electro-optical modulator the authors have furthermore improved the signal-to-noise ratio to an extent where it was possible to measure all coherence terms.In a beam experiment the authors have studied the energy pooling reaction between two laser excited Na* (3p) atoms, where in the final state one of the sodium atoms is in the 5s or 4d state and the other in the ground state. They have determined all eight independent partial cross sections and coherence terms, specified according to the various magnetic substate combinations of the colliding Na* (3p) atoms, as a function of the collision velocity. This is the maximum information that can be extracted from the experiment given the symmetry of the detection scheme. By applying a weak magnetic field, to orient the Na* (3p) atoms, the authors were able to distinguish between the two partial cross sections sigma 11 and sigma 1-1 , where the subscripts 11 and 1-1 refer to the initial magnetic substate combinations of the two collision partners. By using an electro-optical modulator the authors have furthermore improved the signal-to-noise ratio to an extent where it was possible to measure all coherence terms.

Journal of Physics B Atomic Molecular and Optical PhysicsNov 28, 199210 citations

The temperature dependence of the cross section for the energy pooling process Na(3P)+Na(3P)to Na(4D)+Na(3S)

Vlasta Horvatić, Mladen Movre, Cedomil Vadla

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.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.

Journal of Physics B Atomic Molecular and Optical PhysicsOct 14, 19995 citations

Polarization Dependence of Associative Ionization of Laser-Excited Na(3p)P322 Atoms

Joost Kircz, Reinhard Morgenstern, Gerard Nienhuis

The associative ionization ${\mathrm{Na}}^{*}+{\mathrm{Na}}^{*}\ensuremath{\rightarrow}{{\mathrm{Na}}_{2}}^{+}+e$, when Na atoms in a single thermal beam are excited by linearly polarized light, was observed. The ion yield increases by a factor of 1.7 when the light polarization vector is rotated from a perpendicular to a parallel direction with respect to the beam. A theoretical analysis shows that the ionization rates $K$ obey the relations $K(\frac{1}{2}, \frac{3}{2})=0$ and $K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})$ , where the arguments indicate the initial magnetic substates $|{M}_{J}|$ of the two colliding atoms.The associative ionization ${\mathrm{Na}}^{*}+{\mathrm{Na}}^{*}\ensuremath{\rightarrow}{{\mathrm{Na}}_{2}}^{+}+e$, when Na atoms in a single thermal beam are excited by linearly polarized light, was observed. The ion yield increases by a factor of 1.7 when the light polarization vector is rotated from a perpendicular to a parallel direction with respect to the beam. A theoretical analysis shows that the ionization rates $K$ obey the relations $K(\frac{1}{2}, \frac{3}{2})=0$ and $K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})$, where the arguments indicate the initial magnetic substates $|{M}_{J}|$ of the two colliding atoms.

Physical Review LettersMar 1, 198274 citations

Selectivity with respect to the orbital polarization in the energy-pooling process with sodium atoms

I. Yu. Yurova

Cross sections sigma (m 1 m 2 ) nl for the energy pooling processes in the collision between two excited sodium atoms are calculated for the case when the partners are prepared in the 3p-excited states with the definite orbital momentum projections m 1 and m 2 . As a result of the process one of the colliding atoms comes to the ground state and the other partner is excited to nl state with nl=5s, 4d, 4f. The collision velocity is equal to or higher than thermal. The Landau-Zener-locking model (LZ-locking) is developed: the sudden change of the type of the coupling between the electron orbital momentum and the internuclear axis (the locking approximation) is combined with the multicrossing Landau-Zener model. The validity of the LZ-locking model is analysed. The results show strong cross section dependence on the initial quantum numbers m 1 and m 2 , especially in the 5s channel.Cross sections sigma (m 1 m 2 ) nl for the energy pooling processes in the collision between two excited sodium atoms are calculated for the case when the partners are prepared in the 3p-excited states with the definite orbital momentum projections m 1 and m 2 . As a result of the process one of the colliding atoms comes to the ground state and the other partner is excited to nl state with nl=5s, 4d, 4f. The collision velocity is equal to or higher than thermal. The Landau-Zener-locking model (LZ-locking) is developed: the sudden change of the type of the coupling between the electron orbital momentum and the internuclear axis (the locking approximation) is combined with the multicrossing Landau-Zener model. The validity of the LZ-locking model is analysed. The results show strong cross section dependence on the initial quantum numbers m 1 and m 2 , especially in the 5s channel.

Journal of Physics B Atomic Molecular and Optical PhysicsMar 28, 19959 citations

Energy pooling in Na 3p−Na 3p collisions

Vikram S. Kushawaha, Jacob J. Leventhal

The formation of Na ( $\mathrm{nl}$ ) and $\mathrm{Na}_{2}^{}{}_{}{}^{+}$ in sodium vapor (\ensuremath{\sim} ${10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$) irradiated by a single-frequency (20-MHz bandwidth) cw dye laser tuned to one of the $D$ lines has been studied. The dependence of product signal on laser power density suggests that Na $3p$ -Na $3p$ energy pooling collisions are responsible for these species. Rate constants for specific reaction channels and temperature dependences of rate constants are also reported.The formation of Na ($\mathrm{nl}$) and $\mathrm{Na}_{2}^{}{}_{}{}^{+}$ in sodium vapor (\ensuremath{\sim}${10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$) irradiated by a single-frequency (20-MHz bandwidth) cw dye laser tuned to one of the $D$ lines has been studied. The dependence of product signal on laser power density suggests that Na $3p$-Na $3p$ energy pooling collisions are responsible for these species. Rate constants for specific reaction channels and temperature dependences of rate constants are also reported.

Physical Review ADec 1, 198045 citations

K

obey the relations

K(\frac{1}{2}, \frac{3}{2})=0

and

K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})

, where the arguments indicate the initial magnetic substates

|{M}_{J}|

of the two colliding atoms.

The formation of Na (

\mathrm{nl}

) and

\mathrm{Na}_{2}^{}{}_{}{}^{+}

in sodium vapor (\ensuremath{\sim}

{10}^{13}

${\mathrm{cm}}^{\ensuremath{-}3}$) irradiated by a single-frequency (20-MHz bandwidth) cw dye laser tuned to one of the

D

lines has been studied. The dependence of product signal on laser power density suggests that Na

3p

-Na

3p

energy pooling collisions are responsible for these species. Rate constants for specific reaction channels and temperature dependences of rate constants are also reported.