Search for Time Variation of the Fine Structure Constant

An order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant $\alpha$. Applied to a sample of 30 absorption systems, spanning redshifts $0.5<z<\mathrm{}1.6\mathrm{}$, we derive limits on variations in $\alpha$ over a wide range of epochs. For the whole sample, $\Delta \alpha /\alpha =(-1.1\mathrm{}\pm 0.4)\times {10}^{-5\mathrm{}}$. This deviation is dominated by measurements at $z>\mathrm{}1\mathrm{}$, where $\Delta \alpha /\alpha =(-1.9\mathrm{}\pm 0.5)\times {10}^{-5\mathrm{}}$. For $z<\mathrm{}1\mathrm{}$, $\Delta \alpha /\alpha =(-0.2\mathrm{}\pm 0.4)\times {10}^{-5\mathrm{}}$. While this is consistent with a time-varying $\alpha$, further work is required to explore possible systematic errors in the data, although careful searches have so far revealed none.