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 yequivalent tom(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 zsimilar to0.68 to constrain changes in the three parameters over the redshift range 0<zless than or similar to0.68. While the constraints are relatively weak (less than or similar to1 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.