Low energy cosmic-rays (CRs) are responsible for gas heating and ionization of interstellar clouds, which in turn introduces coupling to Galactic magnetic fields. So far the CR ionization rate (CRIR) has been estimated using indirect methods, such as its effect on the abundances of various rare molecular species. Here we show that the CRIR may be constrained from line emission of H₂ rovibrational transitions, excited by CRs. We derive the required conditions for CRs to dominate line excitation, and show that CR-excited lines may be detected with the Very Large Telescope (VLT) over 8 hours integration. Our method, if successfully applied to a variety of clouds at different Galactic locations, will provide improved constraints on the spectrum of low energy CRs and their origins.

低能宇宙射线（CR）负责星际云的气体加热和电离，进而将耦合引入银河磁场。到目前为止，CR离子化率（CRIR）已使用间接方法进行了估算，例如它对各种稀有分子种类的丰度的影响。在这里，我们表明CRIR可能受CR激发的H ₂旋转振动跃迁的线发射的约束。我们推导了CR主导线路激励的必要条件，并表明在8个小时的积分中，甚大望远镜（VLT）可能检测到CR激励的线路。我们的方法如果成功应用于不同银河位置的各种云层，将对低能CR的频谱及其起源提供改善的约束。