We present a comprehensive study of mid-infrared neutral hydrogen (HI) emission lines in 79 nearby (d<200pc) young stars using the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). This work extends accretion diagnostics to mid-infrared HI transitions, which are less affected by extinction and outflow emission compared to optical and near-infrared HI lines. We aim to identify mid-infrared HI transitions that can serve as reliable accretion diagnostics in young stars, and evaluate their utility in deriving physical conditions of the accreting gas. We identify and measure 22 HI transitions in the MIRI wavelength regime (5-28{mu}m) and perform LTE slab modelling to re- move the H_2_O contribution from selected HI transitions. We examine the spatial extent of MIR HI emission and assess contamination from molecular and jet-related emission. We find that mid-IR HI line emission is spatially compact, even for sources with spatially extended [NeII] and [FeII] jets, suggesting minimal contamination from extended jet. Although Pfund {alpha} (HI 6-5) and Humphreys {alpha} (HI 7-6) are the strongest lines in the mid-infrared, they are blended with H2O transitions. This blending necessitates additional processing to remove molecular contamination, thereby limiting their use as accretion diagnostics. Instead, we identify the HI (8-6) at 7.502{mu}m and HI (10-7) at 8.760{mu}m transitions as better alternatives, as they are largely unaffected by molecular contamination and offer a more reliable means of measuring accretion rates from MIRI spectra. We provide updated empirical relations for converting mid-IR HI line luminosities into accretion luminosity for 6 different HI lines in the MIRI wavelength range. Moreover, comparison of observed line ratios with theoretical models shows that MIR HI lines offer robust constraints on the hydrogen gas density in accretion columns, n_H_=10^10.6^ to 10^11.2^cm^-3^ in most stars, with some stars exhibiting lower densities (<10^10^cm^-3^), approaching the optically thin regime.
Cone search capability for table J/A+A/708/A22/tablea1 (Stellar parameters of the nearby YSOs)
