In a previous study [G.-H. Sha, B. Jiang, J.-B. He, C.-H. Zhang, J. Chem. Phys. 102 (1995) 2772], the first evidence for collisional quantum interference (CQI) in intramolecular energy transfer within CO singlet∼triplet mixed states was obtained. We present here another evidence for CQI effect on energy transfer within the singlet∼triplet mixed states of Na 2 ( A 1 Σ + u , v=8 ∼ b 3 Π 0 u , v=14)+Na(3s) by optical–optical double resonance fluorescence spectroscopy. The measured state-to-state cross-sections show the unique feature of abnormal Δ J-dependence of cross-sections due to constructive or destructive interference. Molecular rotation speed and interaction potential have important effect on the extent of interference.