Sensitivity of the HC₅N and HC₇N line intensities to the accuracy of collisional rate coefficients. Each panel shows the line intensities (∫ T_Rdυ) and excitation temperatures (T_ex) of emission lines as a function of frequency. The physical conditions employed in the calculations are n(H₂) = 10⁴ cm⁻³ and T = 10 K. The superscripts ‘CC’ refers to the close-coupling method used in the calculation of the collisional rate coefficients, whereas ‘R3’ and ‘R5’ denote when we employed the HC₃N rate coefficients as template for those of HC₅N and the scattering data for HC₅N as a proxy for HC₇N, respectively. The superscript ‘LTE’ means that the line intensities were derived considering LTE conditions. The shaded region stands for an agreement of 10% with the intensities calculated using CC reference data.