Observed lines in the Orion Bar using the IRAM 30 m telescope. (a1) The tentatively detected N_J = 1₂–0₁ line for SD⁺. The blue line is the convolution of the spectrum with a Gaussian having an FWHM of 1.8 km s⁻¹. (a2) The histogram is obtained by averaging each 400 kHz block of the (a1) spectrum, and the red line is the result of a Gaussian fit. (b) The J = 6–5 line at 256.027 GHz for HCS⁺. (c) The J = 3–2 line at 255.479 GHz for HC¹⁸O⁺. (d) CH₂NH (see text).