We study the isomer-specific photoionisation and photofragmentation of 1,2-dibromoethene (DBE) under strong-field fs-laser irradiation in the gas phase complementing previous studies utilising ns- and ps-laser excitation. Our findings are compatible with a dissociative multiphoton-ionisation mechanism producing a variety of ionic photofragments. Using both Stark deflection and chemical separation of the two isomers, pronounced isomer-specific photofragmentation dynamics could be observed for different product channels. While for Br⁺ formation, the isomer specificity appears to originate from different photoexcitation efficiencies, for the C₂H₂Br⁺ channel it is more likely caused by differences in the coupling to the exit channel. By contrast, the formation of the C₂H₂⁺ photofragment does not seem to exhibit a pronounced isomeric dependence under the present conditions. The present work underlines the importance of isomeric effects in photochemistry even in small polyatomics like the present system as well as their pronounced dependence on the photoexcitation conditions.

我们研究了1,2-二溴乙烯（DBE）在强场飞秒激光照射下的异构体特异性光离子化和光解离过程，补充了之前使用纳秒和皮秒激光激发的研究。我们的发现与通过多光子解离机制产生的各种离子光碎片相兼容。利用斯塔克偏转和化学分离两种异构体的方法，我们观察到了不同产物通道中明显的异构体特异性光解离动力学。在形成Br⁺的过程中，异构体特异性似乎源于不同的光激发效率，而对于C₂H₂Br⁺通道，则更可能是由于与出口通道的耦合差异造成的。相比之下，在当前条件下，C₂H₂⁺光碎片的形成并不表现出明显的异构体依赖性。本研究强调了即使在像目前这种小型多原子体系中，异构效应在光化学中的重要性以及它们对光激发条件的高度依赖性。