Under typical dark cloud conditions, cosmic rays are the primary ionising agent for the interstellar medium and have a crucial influence on the process of star and planet formation.
However, reasonable estimates of the cosmic ray ionisation rate (CRIR) are often difficult to obtain, and the CRIR is strongly influenced by the model assumed.<div>Recently, a new analytical approach to estimate the CRIR in the densest regions of molecular clouds was proposed by <a href="https://ui.adsabs.harvard.edu/abs/2020MNRAS.495L...7B/abstract">Bovino et al. (2020)</a> and applied by <a href="https://ui.adsabs.harvard.edu/abs/2020A%26A...644A..34S/abstract">Sabatini et al. (2020)</a> in the context of the high-mass star formation. The aforementioned method is model-independent and based on the estimate of the H<sub>3</sub><sup>+</sup> column density using its deuterated forms such as H<sub>2</sub>D<sup>+</sup>, which are known to be very abundant in dense and cold star-forming regions.
Taking advantage of the exceptional observational capabilities of ALMA, in this poster, I will present the first high-resolution maps of CRIR in two massive clumps where multiple cores of ortho-H<sub>2</sub>D<sup>+</sup> were observed. I will present these results and the way they provide crucial constraints for chemical/physical modelling of star-forming regions.</div>