Ionization associative

23 Spatial distribution of I- ions detected following K nd-CF3I collisions at intermediate n. The inset indicates the directions of the laser and potassium atom beams 

Associative ionization is the process in which an excited atom collides with either a ground state atom or molecule to form a molecular ion and a free electron. For example, the associative ionization of a K Rydberg atom by collision partner M is represented by 

Ignoring the translational kinetic energy of the collision partners, associative ionization is in fact the only way in which a collision with a ground state atom can ionize a Rydberg atom. 

Associative ionization was also observed between atoms in Sr 5snt states and the ground Sr 5s2 state in a beam of Sr by Worden et al.98 They used multi step resonant laser excitation of the Sr 5sn states, and at Sr number densities of 1013 cm 3, they observed Sr2+. They were able to determine the well depth of Sr2+ to be 0.77 eV. 

Associative ionization measurements have been done with molecules as well. Specifically, associative ionization of K nd states with a variety of molecules has been studied.106 107 K atoms in a thermal beam were excited with pulses formed 

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Dissociative recombination and associative ionization are represented by the forward and backward directions of... 

Conventional associative ionization (AI) occurring at ambient temperature proceeds in two steps excitation of isolated atoms followed by molecular autoionization as the two atoms approach on excited molecular potentials. In sodium for example [44]... 

Figure Cl.4.13. Trap modulation experiment showing much greater deptli of ion intensity modulation (by more tlian one order of magnitude) tlian fluorescence or atom number modulation, demonstrating tliat excited atoms are not tire origin of tire associative ionizing collisions.

Heather R W and Julienne P S 1993 Theory of laser-induced associative Ionization of ultracold Na Phys.Rev. A 47 1887... 

Associative ionization. Occurs when two excited gaseous atoms or molecular moieties interact and the sum of their internal energies is sufficient to produce a single, additive ionic product. 

Non-ionizing electron-neutral interactions create electronically excited neutrals. The ionization reactions occurring when electronically excited neutrals, e.g., noble gas atoms A, collide with ground state species, e.g., some molecule M, can be divided into two classes. [21] The first process is Penning ionization (Eq. 2.6), [22] the second is associative ionization which is also known as the Hombeck-Molnar process (Eq. 2.7). [23]... 

Figure 18. Calculated cross sections and experimental data for He(2J5)-H otouu, total ionization o(Pgl), partial Penning ionization a(AI), partial associative ionization QI, partial formation of quasibound heH + (-o-), quantal calculation 51 (- -), classical calculation.51 Experimental data value obtained with thermal velocity distribution corresponding to average energy of 45 meV 51 value obtained at average energy of 3 + 0 meV I, renormalized data due to Howard et al. 54 x, quantal calculation, thermal average for conditions under which point was obtained.51...

IV. OTHER SPONTANEOUS IONIZATION MECHANISMS A. True Associative Ionization... 

In contrast to the associative process arising in Pgl systems when the ejected electron carries away so much energy that the collision partners cannot separate, we deal in this section with ionization processes that can only occur because energy is gained by formation of a bond between the collision partners after ionization. Such true associative ionization (AI) systems are characterized by the energy conditions... 

Figure 34. Two possible mechanisms for true associative ionization (a) adiabatic path and ionization by dynamic coupling (b) diabatic path and ionization by electronic coupling.

Fig. 11.24 Adiabatic potential curves for the Rb-Rb system. The initially populated Rb nl Rydberg state can lead to associative ionization if its energy at R = exceeds the minimum of the Rb+ + Rb 5s potential well, as shown.

Fig. 11.25 Experimental and theoretical rate constant for associative ionization of Nan + Na 3s atoms at T = 1000 K plotted against effective principal quantum number. Results for 17 < n < 27 (ref. 99) are scaled to absolute results obtained by Boulmer etal. for 5 < n s 15 (ref. 100). Experimental data ns levels ( ) np levels ( ) 2 2 levels (O). Theoretical...

Fig. 11.26 Rb-Rb potential curves showing the origin of the differing rates for Penning and associative ionization. In associative ionization the initial state Rb n( + Rb 5s only is above the lower 2g ionic state at small R where the g - 2U exchange splitting is large. Only at small R does autoionization to the ionic molecular state occur. In contrast, in Penning ionization the initial state Rb n + Rb 5p always lies above the ionic final state, and autoionization can occur at any R.

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