Non-LTE excitation models of SH⁺. The horizontal lines mark the observed line intensities in the Orion Bar. Dotted curves are for a standard model (F = D = 0). Continuous curves are for a model that includes chemical destruction by H atoms and e⁻ (model F, D). Dashed lines are for a model in which destruction rates are multiplied by ten (model F, D × 10). The verticalblack line marks the best model.