N₂H⁺ (black curves, top panels) and N₂D⁺ (black curves, bottom panels) obtained towards the five positions. The IRDC G34.77 central velocity is indicated as a vertical dotted line in all panels. The red curves show the best LTE fitting models obtained by MADCUBA. The green curves show the Gaussian fitting obtained for the isolated component. For the Shock, Ridge, and Clump positions, we report the SiO(2−1) spectra (orange filled) extracted from the ALMA images (Cosentino et al. 2019) towards an angular region consistent with that of our current observations (34″). In the bottom panels, the SiO spectra have been multiplied by 0.2 to allow a more straightforward comparison with the N₂D⁺ spectra.