Kanekar, NCarilli, C LLangston, G IRocha, GCombes, FSubrahamanyan, RStocke, J TMenten, K MBriggs, FranklinWiklind, T2009-08-272010-12-202009-08-272010-12-20Physical Review Letters 95.26 (2005): 261301/1-40031-90071079-7114http://hdl.handle.net/10440/788http://digitalcollections.anu.edu.au/handle/10440/788We have detected the four 18 cm OH lines from the z∼0.765 gravitational lens toward PMN J0134–0931. The 1612 and 1720 MHz lines are in conjugate absorption and emission, providing a laboratory to test the evolution of fundamental constants over a large lookback time. We compare the HI and OH main line absorption redshifts of the different components in the z∼0.765 absorber and the z∼0.685 lens toward B0218+357 to place stringent constraints on changes in F≡gp[α2/μ]1.57. We obtain [ΔF/F]=(0.44±0.36stat±1.0syst)×10-5, consistent with no evolution over the redshift range 0<z≲0.7. The measurements have a 2σ sensitivity of [Δα/α]<6.7×10-6 or [Δμ/μ]<1.4×10-5 to fractional changes in α and μ over a period of ∼6.5  G yr, half the age of the Universe. These are among the most sensitive constraints on changes in μ.4 pageshttp://www.sherpa.ac.uk/romeo/index.php "Author can archive pre-print (ie pre-refereeing) … post-print (ie final draft post-refereeing) … [and] publisher's version/PDF. Link to publisher version … [and] Copyright notice required. Publisher's version/PDF can be used on … employers web site." - from SHERPA/RoMEO site (as at 25/02/10). ©2005 The American Physical SocietyKeywords: Absorbers; Emitters; Gravitational lens; Constraint theory; Gravitation; Lenses; Measurement theory; Astrophysics2005-12-1910.1103/PhysRevLett.95.2613012015-12-11