Vibronic coupling is key to efficient energy flow in molecular systems and a critical component of most mechanisms invoking quantum effects in biological processes. Despite increasing evidence for coherent coupling of electronic states being mediated by vibrational motion, it is not clear how and to what degree properties associated with vibrational coherence such as phase and coupling of atomic motion can impact the efficiency of light-induced processes under natural, incoherent illumination. Here, we show that deuteration of the H₁₁–C₁₁=C₁₂–H₁₂ double-bond of the 11-cis retinal chromophore in the visual pigment rhodopsin significantly and unexpectedly alters the photoisomerization yield while inducing smaller changes in the ultrafast isomerization dynamics assignable to known isotope effects. Combination of these results with non-adiabatic molecular dynamics simulations reveals a vibrational phase-dependent isotope effect that we suggest is an intrinsic attribute of vibronically coherent photochemical processes.

振动耦合是分子系统中有效能量流动的关键，也是大多数在生物过程中引起量子效应的机制的关键组成部分。尽管有越来越多的证据表明振动运动会介导电子态的相干耦合，但尚不清楚与振动相干相关的特性（如原子运动的相位和耦合）如何以及在何种程度上会影响自然，非相干下光诱导过程的效率照明。在这里，我们证明了11-顺式的H ₁₁ -C ₁₁ = C ₁₂ -H ₁₂双键的氘代视觉色素视紫红质中的视网膜发色团显着且出乎意料地改变了光异构化产率，同时在可归因于已知同位素效应的超快异构化动力学中引起了较小的变化。这些结果与非绝热分子动力学模拟的结合揭示了一个振动相位相关的同位素效应，我们认为这是振动相干光化学过程的固有属性。