Figure 1

The PESs of the three lowest electronic states: ${\mathrm{X}}^1{\mathrm{\Sigma }}^{+}$ (black solid curve), ${\mathrm{a}}^3\mathrm{\Pi }$ (red dashed curve), and ${\mathrm{A}}^1\mathrm{\Pi }$ (blue dot-dashed curve). The violet (dot-double-dashed) curve shows the PES of the $2{}^2\mathrm{\Pi }$ resonance state: circles are obtained in the $R$-matrix calculations, the line in the bound-state region is the PES from Ref. [17]. Also, the imaginary part of the CAP (see the text) is drawn with a magenta dotted curve. The inset shows an enlarged view of the CAP (imaginary part) and vibrational function $v=23$ of the ${\mathrm{X}}^1{\mathrm{\Sigma }}^{+}$ state to demonstrate the effect of CAP absorption.

Figure 2

The figure demonstrates derivatives of the eigenphase sum for the ${}^2\mathrm{\Pi }$ symmetry, which are used to derive energies and widths of the resonance. Results from the $R$-matrix calculations are shown by solid curves and the results from the MQDT channel elimination by dashed curves. The results are shown for three different values of $R$: 1.337, 1.437, and 1.537 bohrs. Details of the $R$-matrix calculations can be found in Sec. V of Ref. [28].

Figure 3

The DR cross section for the ground vibronic state of ${\mathrm{CH}}^{+}$ obtained with different sets of parameters of the computational model. The cross sections are computed using the following parameters: (1) $L=10a_0$, $R_0=7a_0$, $\eta =0.030$, $N_v=35$ (solid),

(2) $L=10a_0$, $R_0=7a_0$, $\eta =0.030$, $N_v=30$ (red dot-dashed),

(3) $L=10a_0$, $R_0=8a_0$, $\eta =0.030$, $N_v=35$ (green dotted),

(4) $L=10a_0$, $R_0=7a_0$, $\eta =0.039$, $N_v=35$ (blue dashed), where $N_v$ is the number of vibrational states for each electronic state.

Figure 4

The raw cross section obtained in this study (black thin dashed line) and the one convoluted with experimental uncertainties in the electron beam (black solid line) are compared with experimental measurements by Amitay et al. [35] (thick red solid line) and theoretical results by Takagi et al. [15] (green dashed line), Carata et al. [16] (blue dot-double-dashed line), Chakrabarti et al. [17] (magenta dot-dashed line), and Mezei et al. [18] (violet double-dot-dashed line). Labels of partial waves of the incident electron are assigned to prominent resonances (see Fig. 5). Several excited ionization thresholds ($v=1–4$ of the ${\mathrm{X}}^1{\mathrm{\Sigma }}^{+}$ state and $v=0$ of the ${\mathrm{a}}^3\mathrm{\Pi }$ state) are marked on the top of the figure.

Figure 5

Dominant partial wave contributions $P_{00l\lambda }$ [Eq. (16)] to the total DR probability of ion initially being in the ground vibronic state. (a) $P_{00s\sigma }$, (b) $P_{00p\sigma }$, (c) $P_{00d\sigma }$, (d) $P_{00p\pi }$, (e) $P_{00d\pi }$, (f) $P_{00d\delta }$.