Constraints on changes in fundamental constants from a cosmologically distant OH absorber or emitter

We have detected the four 18 cm OH lines from the z similar to 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 similar to 0.765 absorber and the z similar to 0.685 lens toward B0218+357 to place stringent constraints on changes in F equivalent to g(p)[alpha(2)/mu](1.57). We obtain [Delta F/F]=(0.44 +/- 0.36(stat)+/- 1.0(syst))x10(-5), consistent with no evolution over the redshift range 0 < z less than or similar to 0.7. The measurements have a 2 sigma sensitivity of [Delta alpha/alpha]< 6.7x10(-6) or [Delta mu/mu]< 1.4x10(-5) to fractional changes in alpha and mu over a period of similar to 6.5 G yr, half the age of the Universe. These are among the most sensitive constraints on changes in mu.