Similar levels of deuteration in the pre-stellar core L1544 and the protostellar core HH211

In the centre of pre-stellar cores, deuterium fractionation is enhanced due to low temperatures and high densities. Therefore, chemistry deuterated molecules can be used study earliest stages star formation. We analyse simple molecules, comparing level deuteration in envelopes core L1544 Taurus protostellar HH211 Perseus. single-dish observations CCH, HCN, HNC, HCO$^+$, their $^{13}$C-, $^{18}$O- D-bearing isotopologues, detected with Onsala 20m telescope. derived column densities fractions molecules. Additionally, we radiative transfer simulations results from chemical modelling reproduce observed molecular lines. new collisional rate coefficients for HN$^{13}$C, DNC, DCN that consider hyperfine structure these find levels CCH (10%) both sources, consistent other carbon chains, moderate HCN (5-7%) HNC (8%). The fraction HCO$^+$ towards HH211, most likely caused by isotope-selective photodissociation C$^{18}$O. Similar show process equally efficient suggesting envelope still retains composition original core. fact two cores are embedded different clouds also suggests environmental conditions do not have a significant effect on within dense cores. Radiative shows it necessary include outer layers effects extended structures. Besides observations, require presence an diffuse layer where relatively abundant.