Low-energy elastic scattering of positrons by ${\mathrm{O}}_2$

We employed the method of continued fractions in conjunction with the positron correlation polarization potential model with different levels of polarization to calculate the elastic integral and differential cross sections for positron scattering by ${\mathrm{O}}_2$ molecules. We show how the addition of higher-order terms in the polarization interaction is necessary in order to achieve convergence of the scattering potential. Also, we present the effect that such terms have over the integral cross sections, comparing with results of previous studies. When convergence of the scattering potential is attained, the resulting cross sections fairly agree with the most recent total cross section measurements up to the positronium formation threshold and moreover exhibit good agreement with the available experimental quasielastic differential cross sections.

Figure 1

Spherical components of the scattering potential; see Eq. (1). Legends are as follows: dashed-double-dotted line, static; dashed-dotted line, PCOP; dotted line, PQ; dashed line, PB; solid line, PG. The inset shows how different polarization potential affects the matching radius ($r_c$). Note that the solid and dashed lines are practically merged.

Figure 2

Elastic integral cross section showing the contribution of each correction term present in the polarization potential [see Eq. (16)]. Theoretical approaches: solid line, PG; dashed line, PB; dotted line, PQ; dashed-dotted line, PCOP; dashed-double-dotted line, IAM-SCAR of Chiari et al. [14]. Experimental data: solid circles, Chiari et al. [14]; triangles, Charlton et al. [5]; inverted triangles, Dababneh et al. [7]; diamonds: Marler [13]; squares, Coleman et al. [3].

Figure 3

Differential cross section for 4.0 eV. Legends are as follows: solid line, PG; dashed line, PB; dotted line, PQ; dashed-dotted line, PCOP. Experimental data from Przybyla et al. [12].

Figure 4

Differential cross section for 6.75 eV. Legends are the same as Fig. 3.

Figure 5

Differential cross section for 10.0 eV. Legends are the same as Fig. 3.

Figure 6

Differential cross section for 20.0 eV. Legends are the same as Fig. 3.

Figure 7

Differential cross section for 50.0 eV. Legends are the same as Fig. 3.

Figure 8

Differential cross section for 100.0 eV. Legends are the same as Fig. 3.