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Supernova remnants (SNRs) may regulate star formation in galaxies. Forexample, SNR-driven shocks may form new molecular gas or compress pre-existingclouds and trigger the formation of new stars. To test this scenario, wemeasure the deuteration of $N_2H^+$, $D_{frac}^{N_2H^+}$, a well-studied tracerof pre-stellar cores, across the Infrared Dark Cloud (IRDC) G034.77-00.55,known to be experiencing a shock interaction with the SNR W44. We useN$_2$H$^+$ and N$_2$D$^+$ J=1-0 single pointing observations obtained with the30m antenna at the Instituto de Radioastronomia Millimetrica to infer$D_{frac}^{N_2H^+}$ toward five positions across the cloud, namely a massivecore, different regions across the shock front, a dense clump and ambient gas.We find $D_{frac}^{N_2H^+}$ in the range 0.03-0.1, several orders of magnitudelarger than the cosmic D/H ratio ($\sim$10$^{-5}$). Across the shock front,$D_{frac}^{N_2H^+}$ is enhanced by more than a factor of 2($D_{frac}^{N_2H^+}\sim$0.05-0.07) with respect to the ambient gas ($\leq$0.03)and similar to that measured generally in pre-stellar cores. Indeed, in themassive core and dense clump regions of this IRDC we measure$D_{frac}^{N_2H^+}$}$\sim$0.1. We find enhanced deuteration of $N_2H^+$ acrossthe region of the shock, at a level that is enhanced with respect to regions ofunperturbed gas. It is possible that this has been induced by shockcompression, which would then be indirect evidence that the shock is triggeringconditions for future star formation. However, since unperturbed dense regionsalso show elevated levels of deuteration, further, higher-resolution studiesare needed to better understand the structure and kinematics of the deuteratedmaterial in the shock region, e.g., if it still in relatively diffuse form oralready organised in a population of low-mass pre-stellar cores.

Deuterium Fractionation across the Infrared Dark Cloud G034.77-00.55 interacting with the Supernova Remnant W44