Limit on the Cosmological Variation of mp/me from the Inversion Spectrum of Ammonia

We obtain the limit on the space-time variation of the ratio of the proton mass to the electron mass, μ=mp/me, based on comparison of quasar absorption spectra of NH3 with CO, HCO+ and HCN rotational spectra. For the inversion transition in NH3 (λ≅1.25 cm-1) the relative frequency shift is significantly enhanced: δω/ω=-4.46δμ/μ. This enhancement allows one to increase sensitivity to the variation of μ using NH3 spectra for high redshift objects. We use published data on microwave spectra of the object B0218+357 to place the limit δμ/μ=(0.6±1.9)x10-6 at redshift z=0.6847; this limit is several times better than the limits obtained by different methods and may be significantly improved. Assuming linear time dependence we obtain μ/μ=(-1±3)x10-16 yr-1