Constraining the variation of fundamental constants using 18 cm OH lines.

We describe a new technique to estimate variations in the fundamental constants using 18 cm OH absorption lines, with the advantage that all lines arise in the same species, allowing a clean comparison between the measured redshifts. In conjunction with one additional transition, it is possible to simultaneously measure changes in alpha, g(p), and y identical with m(e)/m(p). We use the 1665 and 1667 MHz line redshifts in conjunction with those of HI 21 cm and mm-wave molecular absorption in a gravitational lens at z approximately 0.68 to constrain changes in the three parameters over the redshift range 0<z less, similar 0.68. While the constraints are relatively weak ( less, similar 1 part in 10(3)), this is the first simultaneous constraint on the variation of all three parameters. Either one (or more) of alpha, g(p), and y must vary with cosmological time or there must be systematic velocity offsets between the OH, HCO+, and HI absorbing clouds.