A search for the space-time variations in the proton-to-electron mass ratio using the [Fe II] transitions

A new limit in the spatial and temporal variations in the proton-to-electron mass ratio (Δμ/μ) was found from an analysis of the combined 27 Ritz wavelengths of [Fe II] lines found in the quasar spectra together with laboratory data. The obtained result was . This will allow us to check for the space-time variation limits of Δμ/μ over cosmic timescales and develop future improvements in this limit with high redshifts of quasi-stellar objects (QSOs).