$B$-spline $R$-matrix-with-pseudostates approach for excitation and ionization of atomic oxygen by electron collisions

Electron scattering with atomic oxygen has been studied using the $B$-spline $R$-matrix-with-pseudostates method. Cross sections for elastic scattering, excitation, emission, and ionization processes are presented. The excitation cross sections have been calculated for transitions between the $2s^{2}2p^4$ and $2s^{2}2p^{3}3l$ states of oxygen in the energy range from threshold to 200 eV. The present work differs from numerous previous studies due to the inclusion of a large number of pseudostates in the calculation. We included a total of 1116 spectroscopic bound, core-excited autoionizing, and target continuum states in the close-coupling expansion. The atomic oxygen structure model has been described by combining the multiconfiguration Hartree-Fock and the $B$-spline box-based multichannel methods. The inclusion of a large number of pseudostates representing the target continuum has a major impact, especially on the theoretical prediction of the excitation cross sections for many transitions at intermediate energies. A large reduction in excitation and emission cross sections has been noted due to the inclusion of coupling to the ionization continuum. The calculated cross sections are now in better agreement with available experimental results. The ionization cross sections for the ground $2s^{2}2p^4{}^{3}P$ and metastable $2s^{2}2p^4{}^{1}D$ and ${}^{1}S$ states are also presented. The electron-impact-induced emission cross sections for the $\left(2s^{2}2p^{3}3s\right){}^3{S}^o–\left(2s^{2}2p^4\right){}^{3}P$ (130.4 nm), $\left(2s^{2}2p^{3}3d\right){}^3{D}^o–\left(2s^{2}2p^4\right){}^{3}P$ (102.7 nm), $\left(2s^{2}2p^{3}3s^{\prime }\right){}^3{D}^o–\left(2s^{2}2p^4\right){}^{3}P$ (98.9 nm), and $\left(2s^{2}2p^{3}3s^{\prime \prime }\right){}^3{D}^o–\left(2s^{2}2p^4\right){}^{3}P$ (87.8 nm) transitions have been calculated and compared with the available experimental results.

Figure 1

Angle-integrated cross sections for elastic electron scattering from oxygen atoms in their $\left(2p^4\right){}^{3}P$ ground state. The present BSR-1116 results are compared with the BSR-67 calculation [28], with the calculation of Plummer et al. [12] (RM-191), and with the experimental data of Williams and Allen [29]. The momentum-transfer cross sections are also shown.

Figure 2

Angle-integrated cross sections for elastic electron scattering from oxygen atoms in the metastable $\left(2p^4\right){}^{1}D$ states. The current BSR-1116 results are compared with those from a BSR-26 model [8]. The momentum-transfer cross sections are also shown.

Figure 3

Angle-integrated cross sections for elastic electron scattering from oxygen atoms in the metastable $\left(2p^4\right){}^{1}S$ states. The current BSR-1116 results are compared with those from a BSR-26 model [8]. The momentum-transfer cross sections are also given.

Figure 4

The excitation cross sections for the forbidden $\left(2p^4\right){}^{3}P–\left(2p^4\right){}^{1}D$ transition. The present BSR-1116 results are compared with those from a BSR-26 model [8] and a six-state $R$ matrix with polarized pseudostates (RM-6) [12]. Also shown are experimental data of Shyn et al. [31] and Doering [32].

Figure 5

The excitation cross sections for the forbidden $\left(2p^4\right){}^{3}P–\left(2p^4\right){}^{1}S$ transition. The present BSR-1116 results are compared with those from a BSR-26 model [8] and a six-state $R$ matrix with polarized pseudostates (RM-6) [12]. Also shown are experimental data of Shyn et al. [31] and Doering and Gulcicek [33].

Figure 6

The excitation cross sections for the forbidden $\left(2p^4\right){}^{1}D–\left(2p^4\right){}^{1}S$ transition. The present BSR-1116 results are compared with those from a BSR-26 model [8] and a six-state $R$ matrix with polarized pseudostates (RM-6) [12].

Figure 7

The excitation cross sections for the allowed $\left(2p^4\right){}^{3}P–\left(2p^{3}3s\right){}^3{S}^o$ transition. The present BSR-1116 results are compared with those from a BSR-26 model [8], a 52-state RMPS calculation (RMPS-52) [11], a CCO calculation of Wang and Zhou [42], and experimental data of Vaughan and Doering [37], Kanik et al. [40], and Johnson et al. [41]. The recommended cross sections from Johnson et al. [7] are also shown.

Figure 8

The excitation cross sections for the allowed $\left(2p^4\right){}^{3}P–\left(2p^{3}3s^{\prime }\right){}^3{D}^o$ transition. The present BSR-1116 results are compared with those from a BSR-26 model [8], a 52-state RMPS calculation (RMPS-52) [11], and experimental data of Vaughan and Doering [37] and Kanik et al. [40].

Figure 9

The excitation cross sections for the allowed $\left(2p^4\right){}^{3}P–\left(2p^{3}3s^{\prime \prime }\right){}^3{P}^o$ transition. The present BSR-1116 results are compared with those from a BSR-26 model [8], a 52-state RMPS calculation (RMPS-52) [11], and experimental data of Vaughan and Doering [43] and Kanik et al. [40].

Figure 10

The excitation cross sections for the allowed $\left(2p^4\right){}^{3}P–\left(2p^{3}3d\right){}^3{D}^o$ transition. The present BSR-1116 results are compared with those from the BSR-8, BSR-16, and BSR-26 models [8], the 52-state RMPS calculations (RMPS-52) [11], and experimental data of Vaughan and Doering [43] and Kanik et al. [40].

Figure 11

The excitation cross sections for the $\left(2p^4\right){}^{3}P–\left(2p^{3}3p\right){}^{3}P$ transition as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8] and experimental data of Gulcicek et al. [45].

Figure 12

The excitation cross sections for the $\left(2p^4\right){}^{3}P–\left(2s2p^5\right){}^3{P}^o$ transition as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8], a 52-state RMPS calculation (RMPS-52) [11], and experimental data of Vaughan and Doering [43].

Figure 13

The $\left(2p^4\right){}^{3}P–\left(2p^{3}3s\right){}^5{S}^o$ excitation cross sections as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8] and experimental data of Doering and Gulcicek [46].

Figure 14

The excitation cross sections for the $\left(2p^4\right){}^{3}P–\left(2p^{3}3p\right){}^{5}P$ transition as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8] and experimental data of Gulcicek et al. [45].

Figure 15

The $\left(2p^{3}3s\right){}^3{S}^o–\left(2p^4\right){}^{3}P$ emission cross sections as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8] and experimental data of Wang and McCokey [49], Zipf and Erdman [48], Doering and Yang [39], Noren et al. [50], and Johnson et al. [47].

Figure 16

The $\left(2p^{3}3d\right){}^3{D}^o–\left(2p^4\right){}^{3}P$ emission cross sections as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8] and experimental data of Zipf and Erdman [48], Wang and McConkey [49], and Johnson et al. [47].

Figure 17

The $\left(2p^{3}3s^{\prime }\right){}^3{D}^o–\left(2p^4\right){}^{3}P$ emission cross sections as a function of electron energy. The present BSR-1116 results are compared with those from a BSR-26 model [8] and experimental data from Zipf and Erdman [48], Wang and McConkey [49], and Johnson et al. [47].

Figure 18

The $\left(2p^{3}3s^{\prime \prime }\right){}^3{P}^o–\left(2p^4\right){}^{3}P$ emission cross sections as a function of electron energy. The present BSR-1116 results are shown with and without cascade contributions, and compared with experimental data of Wang and McConkey [49] and Johnson et al. [47].

Figure 19

Angle-integrated cross sections for electron-impact ionization of oxygen atoms in their $\left(2p^4\right){}^{3}P$ ground state. The present BSR-1116 results are compared with the BEB predictions of Kim and Desclaux [53], the CCO calculations of Wang and Zhou [42], and the experimental data of Brook et al. [51] and Thompson et al. [52]. The direct ionization cross sections and the partial contribution of the $2s$ ionization are also shown.

Figure 20

Angle-integrated cross sections for electron-impact ionization of oxygen atoms in the metastable state $\left(2p^4\right){}^{1}D$. The direct ionization cross sections and the partial contribution of the $2s$ ionization are also shown.

Figure 21

Angle-integrated cross sections for electron-impact ionization of oxygen atoms in the metastable $\left(2p^4\right){}^{1}S$ state. The direct ionization cross sections and the partial contribution of the $2s$ ionization are also shown.

Figure 22

Angle-integrated elastic, elastic + excitation, and grand total (elastic + excitation + ionization) cross sections for electron collisions with oxygen atoms in their $\left(2p^4\right){}^{3}P$ ground state. The experimental results of Williams and Allen [29] and theoretical data of Joshupura et al. obtained from the complex potential (CP) method [55] have also been shown.

Figure 23

Angle-integrated elastic, elastic + excitation, elastic + excitation + ionization, and grand total cross sections for electron collisions with oxygen atoms in their $\left(2p^4\right){}^{1}D$ metastable state. In this case, the grand total cross sections also contain deexcitation through superelastic scattering.

Figure 24

Angle-integrated elastic, elastic + excitation, elastic + excitation + ionization, and grand total cross sections for electron collisions with oxygen atoms in their $\left(2p^4\right){}^{1}S$ metastable state. In this case, the grand total cross sections also contain deexcitation through superelastic scattering.