Figure 1

(Color online) The quantum defects of the electronic states included in the present study as a function of the bending angle $\theta$ for fixed $R_{\mathrm{CH}}=2.0\mathrm{a}.\mathrm{u}.$ and $R_{\mathrm{CO}}=2.0877\mathrm{a}.\mathrm{u}.$ Labeling the states with electronic momentum projection $\lambda$ is an approximation and for large values of $\theta$ it is not appropriate. However, the four $s\sigma$, $p\sigma$, $d\sigma$, and $p{\pi }^{\prime }$ states are always uncoupled from $p{\pi }^{″}$ states for nonlinear geometries. In the absence of the nondiagonal matrix elements in Eq. (1) the $p{\pi }^{\prime }$ and $p{\pi }^{″}$ states would have the same quantum defects. The Renner-Teller parameters are completely determined by the geometry dependence of $p\pi$ and $p\sigma$ defects [Eq. (6)].Reuse & Permissions

Figure 2

(Color online) Several adiabatic potential curves for the ${\mathrm{HCO}}^{+}$ ion as a function of the $R_{\mathrm{CH}}$ distance for different projections $m_{\phi }$ of the vibrational angular momentum. The curves of the same color correspond to the vibrational states with the same quantum number $m_{\phi }$ but different $L$. The energies of the lowest vibrational states with $m_{\phi }=0$ and $m_{\phi }=\pm 1$ are shown by two horizontal lines.Reuse & Permissions

Figure 3

(Color online) The figure shows the present theoretical DR cross section (dashed and dotted-dashed lines) for ${\mathrm{HCO}}^{+}$ as a function of the incident energy $E$. The initial vibrational state is the ionic ground state for the dotted-dashed curve and the first excited state for the dashed curve. The experimental [21] (cross symbols) and previous theoretical [31] (thin solid line) cross sections are also shown for comparison. The theoretical curves include the averaging over the electron energy distribution according to the procedure described by Eq. 2 of Ref. 34 with $\mathrm{\Delta }{E}_{\perp }=\mathrm{\Delta }{E}_{\mid \mid }=3\mathrm{meV}$.Reuse & Permissions

Figure 4

(Color online) Theoretical and experimental DR thermal rates for ${\mathrm{HCO}}^{+}$. The dotted-dashed and dashed lines are the theoretical rates obtained for the ground and first excited vibrational states of the ion. The experimental rate (solid line) is obtained from the experimental cross section, Ref. 21. The results from a number of other experiments with ${\mathrm{HCO}}^{+}$ [22, 23, 24, 25, 26, 27, 28, 29, 30] are also shown.Reuse & Permissions

Figure 5

(Color online) Resonance potential curves $U_a\left(R_{\mathrm{CH}}\right)$ of the neutral molecule states having magnetic quantum number $M=1$. The potential curves were calculated in the energy range where at least one electron-ion channel $U_i^{+}\left(R_{\mathrm{CH}}\right)$ (for the given $R_{\mathrm{CH}}$) is open. Thus, the lower bound of the calculated curves corresponds to the ground potential curve $U_{0,0}^{+}\left(R_{\mathrm{CH}}\right)$ of the ion. The potential curves of the ion are also shown by dashed thick lines (see also Fig. 2). The Rydberg series are crowded just below the ionic potential curves. For clarity, visible gaps between the Rydberg series and the ionic curves have been intentionally introduced artificially, to show the behavior of the resonance curves belonging to higher ionic channels. The horizontal line represents the energy of the ground vibrational level.Reuse & Permissions

Figure 6

(Color online) A part of the spectrum of Fig. 5 showing the interval of $R_{\mathrm{CH}}$ corresponding to the left turning point of the vibrational motion. For convenience, the energy of the ground ionic curve $U_{0,0}^{+}\left(R_{\mathrm{CH}}\right)$ was subtracted from all the data. In the figure, curves with positive and small negative slopes correspond to Rydberg states converging to the nearest ionic thresholds. The probability to capture the electron tends to be high for such states, diminishing however at high principal quantum numbers as $n_c^{-3}$. Arrows indicate splittings for a few avoided crossings.Reuse & Permissions