H₂ excitation conditions along the redshifted lobe axis. Panel a: surface brightness of H₂ 1−0 S(1) averaged across the lobe, not corrected for extinction, as a function of deprojected distance from the source. Panel b: average extinction at 2.12 μm obtained from the line ratio H₂ 1−0 Q(7)/1−0 S(5) (see text). Panel c: H₂ excitation temperature obtained by fitting the excitation diagram. Panel d: H₂ column density calculated from the same excitation diagrams (see Appendix F).