Transitions of HOCS⁺ detected towards the G+0.693−0.027 molecular cloud (listed in Table 2). We depict with a red line the result of the best LTE fit of HOCS⁺, while the blue line plots the emission from all the molecules identified to date in our survey. The observed spectra are plotted as gray histograms. Note that for the K_a = 0 transitions, HOCS⁺ appears to be blended with HNC³⁴S because of their similar B + C, but the contribution of HNC³⁴S can be well constrained based on the HNC³²S/HNC³⁴S isotopic ratio (Sanz-Novo et al. 2024a).