scholarly journals Velocity Dependence of Rotationally Inelastic Cross-Sections

1988 ◽  
Vol 9 (4-6) ◽  
pp. 219-240 ◽  
Author(s):  
Christopher P. Fell ◽  
Anthony J. McCaffery ◽  
Katharine L. Reid ◽  
Anton Ticktin ◽  
Benjamin J. Whitaker
Keyword(s):  
Energy Dependence ◽  
Cross Sections ◽  
Velocity Vector ◽  
Rotational Energy ◽  
Velocity Spread ◽  
Narrow Linewidth ◽  
Rotational Energy Transfer ◽  
State Transfer ◽  
Thermal Cell ◽  
Velocity Selection

Techniques are described for obtaining the energy-dependence of state to state rotational energy transfer (RET) cross-sections in thermal cell experiments through velocity selection by Doppler shift. The case of polarised excitation and detection is discussed in detail and expressions presented which enable the state multipoles of population, orientation and alignment to be obtained from appropriate RET experiments. It is found that the translational order present in a non-isotropic collision environment, such as that resulting from excitation with a narrow linewidth laser, causes state multipoles of different rank to become coupled. Experimental results are presented for the energy dependence of cross-sections for state to state transfer of population and of orientation in Li2-Xe collisions. The way the relative velocity vector changes as a result of a collision may also in principle be studied using a high resolution probe (e.g. a second laser) of the velocity spread following RET.

Temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer and for quenching in cesium, induced in collisions with H2, N2, CH4, and CD4

1982 ◽  
Vol 60 (2) ◽  
pp. 239-244 ◽  
Author(s):  
I. N. Siara ◽  
R. U. Dubois ◽  
L. Krause
Keyword(s):  
Energy Transfer ◽  
Temperature Dependence ◽  
Cross Sections ◽  
Rotational Energy ◽  
Excitation Transfer ◽  
Sensitized Fluorescence ◽  
Temperature Range ◽  
Rotational Energy Transfer ◽  
Order Of Magnitude

The temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer in cesium, as well as the effective quenching of these states, induced in collisions with H2, N2, CH4, and CD4 molecules have been investigated in a series of sensitized fluorescence experiments over a temperature range 390–640 K. The 72P mixing cross sections are of the order of 10−15 cm2 and exceed by at least one order of magnitude similar cross sections for mixing by collisions with Ne, Ar, Kr, and Xe. The large sizes of the mixing cross sections and their variation with temperature are ascribed to a phenomenon of electronic-to-rotational energy transfer.

Inelastic Collisions Between Excited Alkali Atoms and Molecules X. Temperature Dependence of Cross Sections for 2P1/2↔2P3/2 Mixing in Cesium, Induced in Collisions with Deuterated Hydrogens, Ethanes, and Propanes

1974 ◽  
Vol 52 (7) ◽  
pp. 589-591 ◽  
Author(s):  
E. Walentynowicz ◽  
R. A. Phaneuf ◽  
L. Krause
Keyword(s):  
Energy Transfer ◽  
Temperature Dependence ◽  
Isotope Effect ◽  
Cross Sections ◽  
Rotational Energy ◽  
Inelastic Collisions ◽  
Atoms And Molecules ◽  
Rotational Energy Transfer ◽  
Alkali Atoms ◽  
The Cross

The dependence on temperature of the cross sections for 2P1/2 ↔ 2P3/2 mixing in cesium, induced in collisions with various deuterated hydrogen, ethane and propane molecules, has been studied in the range 290–650 K. In the cases of hydrogen and ethane, the behavior of the cross sections was found to depend on the degree of deuteration of the molecules. The very large sizes of the mixing cross sections and the isotope effect observed in their variation with temperature, are ascribed to the phenomenon of electronic to rotational energy transfer.

Rotational Energy Transfer within the A1Σu+ State of Na2 Induced by Collisions with (2S1/2) Na

2007 ◽  
Vol 62 (3-4) ◽  
pp. 176-178
Author(s):  
Rami Haj Mohamad ◽  
Khaled Hussein ◽  
Abdel-Monhem Nachabé
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Rhodamine 6G ◽  
Rotational Energy ◽  
Spectral Lines ◽  
Rotational Energy Transfer ◽  
Rotational Transitions ◽  
Electronic Ground

The (v’ = 34, J’ = 14) level of the A1Σ+u electronic state of Na2 has been selectively populated by excitation with the 578.1 nm line of a ring dye-laser with rhodamine 6G. Through collisions with (2S1/2) Na atoms, energy is transferred to neighbouring rotational levels in Na2, and the density of these levels is determined by observing the fluorescence to the electronic ground state. From previous measurements of the lifetime of the A1Σ+u state and new measurements of the intensities of collision-induced spectral lines, absolute collision cross-sections for all rotational transitions up to ΔJ = ±6 have been obtained; the total cross-section for all rotational transitions observed is: rotσtotal = 0.41 nm2.

Assessment of the Accuracy of the Quasiclassical Trajectories Approximation at a Low Collision Energy for the He — N2 System

1987 ◽  
Vol 42 (7) ◽  
pp. 731-734 ◽  
Author(s):  
Aristophanes Metropoulos
Keyword(s):  
Energy Transfer ◽  
Cross Sections ◽  
Differential Cross ◽  
Collision Energy ◽  
Rotational Energy ◽  
Quasiclassical Approximation ◽  
Differential Cross Sections ◽  
Close Coupling ◽  
Rotational Energy Transfer ◽  
Quasiclassical Trajectories

We have computed rotational energy transfer differential and state-to-state integral quasiclassical cross sections for the He - N2 system at 27.3 meV. By comparing these differential cross sections to close coupling ones, the accuracy of the quasiclassical approximation at such a low collision energy has been assessed as satisfactory.

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