From CISS to TRANS: A Molecular Analog of Chiral-Induced Spin Selectivity

Chiral-induced spin selectivity (CISS) describes how electron transmission through chiral systems can spontaneously polarize spin populations. Here, we demonstrate an analogous phenomenon, termed TRANS (Total Rotational-Angular Momentum Selectivity), emerging in gas-phase radical–molecule collisions. Using nitric oxide (NO) as a spin–orbit-active probe, we investigate the vibrationally mediated dissociation of NO–(2-butanol) collision complexes prepared under molecular beam conditions. Infrared action spectroscopy combined with resonance-enhanced multiphoton ionization and velocity map imaging reveals that the NO product distributions depend on both the handedness of the chiral partner and the initially prepared vibrational mode. These enantioselective spin–orbit and Λ-doublet populations reflect how Berry forces and pseudo Jahn–Teller coupling near avoided crossings encode molecular chirality into electronic angular momentum. Comparison between racemic and enantiopure NO–(2-butanol) complexes establishes molecular benchmarks for understanding how chiral topology governs nonadiabatic energy flow. This work extends the conceptual framework of CISS into the domain of transient, collision-induced dynamics in isolated molecular systems, highlighting TRANS as a molecular platform to probe chirality-angular momentum correlations and explore the role of topology in spin-dependent chemical reactivity.