Do state-to-state propensity rules for vibrational energy transfer remain valid in the intermediate state density region?

State-to-state branching ratios are reported for vibrational energy transfer (VET) from the 8² and 7¹8¹ levels in S₁ ρ{variant}-difluoro-benzene by He and H₂ in a supersonic free jet expansion. 8² is in the sparse region of the vibrational manifold (E_vib=350 cm^-1; ρ{variant}_vib≈0.05 states / cm^-1) while 7¹8¹ is in the intermediate state density region (E_vib=751 cm^-1; p_vib≈0.4 states / cm^-1). Two principal results emerge: (i) the propensity rules that apply for 8² (sparse region) are not followed for 7¹8¹ (intermediate region) and (ii) He and H₂ show virtually identical state-to-state branching ratios for 8₂ but not for 7¹8¹.