Low-energy electron scattering from methylene radicals: Multichannel-coupling effects

We reported elastic (integrated and differential), momentum-transfer, and excitation cross sections for electron collisions with methylene radical. $R$-matrix method is employed to calculate the cross section for electron energies ranging from 0.01 to 15 eV. The results of 1-state, 3-state, 15-state, 20-state, and 24-state close-coupling (CC) approximations are presented. We detect two shape resonances and three Feshbach resonances in the 24-state CC approximation. We discuss the multichannel-coupling effects on the calculated cross sections and resonances, and how the number of excited states included in the target state impacts the convergence of the elastic and the $X{}^3{B}_1\to 1{}^{1}A_1$ and $X{}^3{B}_1\to 1{}^1{B}_1$ excitation cross sections, especially at higher impact energy. Finally, we estimate the accuracy of the $1{}^{1}A_1$ and $1{}^1{B}_1$ excitation cross sections.

Figure 1

Elastic cross section for 1-state, 3-state, 15-state, 20-state, and 24-state CC calculations in the energy range of 0.01–15 eV.

Figure 2

Elastic cross sections in the energy range of 0.01–15 eV. (a) Doublet $A_1, B_1, B_2$, and $A_2$ components and total doublets. (b) Quadruplet $A_1, B_1, B_2$, and $A_2$ components and total quadruplets. (c) Total doublets, total quadruplets, total doublet plus total quadruplet (Sum), Born correction, and Born corrected.

Figure 3

(a) $X{}^{3}B^1\to 1{}^{1}A_1$ excitation cross sections, (b) $X{}^{3}B^1\to 1{}^{1}B_1$ excitation cross sections, and (c) $X{}^{3}B^1\to 2{}^{1}A_1$ excitation cross sections.

Figure 4

The excitation cross sections in five different models: 3-state, 15-state, 15-state (with a smaller CAS), 20-state, and 24-state CC calculations. (a) $X{}^{3}B^1\to 1{}^{1}A_1$ excitation cross sections. The 15-state excitation threshold has been shifted lower by 0.28 eV. (b) $X{}^{3}B^1\to 1{}^{1}B_1$ excitation cross sections. The 15-state excitation threshold has been shifted lower by 0.25 eV.

Figure 5

Difference cross sections of doublet symmetry for elastic scattering at incident energies of 2, 4, 10, 12, and 15 eV with five different models: 1-state, 3-state, 15-state, 20-state, and 24-state CC calculations.

Figure 6

Total difference cross sections for elastic scattering at incident energies of 2, 4, 10, 12, and 15 eV for the 24-state CC model.

Figure 7

State-resolved differential cross sections at 2.0 eV.

Figure 8

Momentum transfer cross section in the energy range of $0.01–\text{15}$ eV.