Rotational transitions induced by collisions of ${\mathrm{HD}}^{+}$ ions with low-energy electrons

A series of computations based on multichannel quantum defect theory have been performed in order to produce the cross sections of rotational transitions (excitations $N_i^{+}-2\to$ $N_i^{+}$, deexcitations $N_i^{+}$ $\to$ $N_i^{+}-2$, with $N_i^{+}=2$ to 10) and of their competitive process, the dissociative recombination, induced by collisions of ${\mathrm{HD}}^{+}$ ions with electrons in the energy range ${10}^{-5}$ to 0.3 eV. Maxwell anisotropic rate coefficients, obtained from these cross sections in the conditions of the Heidelberg Test Storage Ring (TSR) experiments $(k_B{T}_t=2.8$ meV and $k_B{T}_l=45$ $\mu$eV), have been reported for those processes in the same electronic energy range. Maxwell isotropic rate coefficients have been presented as well for electronic temperatures up to a few hundred Kelvins. Very good overall agreement is found between our results for rotational transitions and the former theoretical computations as well as with experiment. Furthermore, due to the full rotational computations performed, the accuracy of the resulting dissociative recombination cross sections is improved considerably.

Figure 1

Cross sections for rotational excitations $N_i^{+}-2\to$ $N_i^{+}$, with $N_i^{+}=2$ to 9, in the ground vibrational state of ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$. Black solid curves: MQDT computations; red dashed curves: ANR approximation-based computations.

Figure 2

Zoom in the linear scale of the cross section for the transition 0 $\to$ 2, in the ground vibrational state of ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$. Black solid curve: MQDT computations; red dashed curve: ANR approximation-based computations.

Figure 3

Rate coefficients of the rotational excitations $N_i^{+}-2\to$ $N_i^{+}$, with $N_i^{+}=2$ to 5, and reverse reactions, for the ground vibrational state of ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$. Black solid curves: MQDT computations; red dashed curves: ANR approximation-based computations.

Figure 4

Rate coefficients of the rotational excitations $N_i^{+}-2\to$ $N_i^{+}$, with $N_i^{+}=6$ to 10, and reverse reactions for the ground vibrational state of ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$. Black solid curves: MQDT computations; red dashed curves: ANR approximation-based computations.

Figure 5

Cross sections for the dissociative recombination of vibrationally relaxed ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$ on initial rotational levels $N_i^{+}=0$ to 5 for electron collision energy in the range 0–24 meV.

Figure 6

Cross sections for the dissociative recombination of vibrationally relaxed ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$ on initial rotational levels $N_i^{+}=0$ to 5 for electron collision energies in the range 0–300 meV.

Figure 7

Maxwell anisotropic rate coefficients for the dissociative recombination of vibrational relaxed ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$ on its initial rotational levels $N_i^{+}=0$ to 5 as in Refs. [31, 32, 33].

Figure 8

Scaled rate coefficients for the dissociative recombination of ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$ at different experimental temperatures assumed for the rotational distribution of the ions in the storage ring, compared to former computations and experiment [33].

Figure 9

Maxwell isotropic rate coefficients for the dissociative recombination ${\mathrm{HD}}^{+}\left(X{}^2{\Sigma }_g^{+}\right)$ with $v_i^{+}=0$ as a function of initial rotational level, $N_i^{+}=0$ to 10 .