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We present the first detection of OH absorption in diffuse gas at $z>0$,along with another eight stringent limits on OH column densities for coldatomic gas in galaxies at $0<z<0.4$. The absorbing gas detected towardsQ0248+430 ($z_q$=1.313) originates from a tidal tail emanating from a highlystar forming galaxy G0248+430 ($z_g$=0.0519) at an impact parameter of 15 kpc.The measured column density is $N$(OH) =(6.3$\pm$0.8)$\times$10$^{13}$($\frac{T_{\rm ex}}{3.5}$)($\frac{1.0}{f_c^{\rmOH}}$) cm$^{-2}$, where $f_c^{\rm OH}$ and $T_{\rm ex}$ are the covering factorand the excitation temperature of the absorbing gas, respectively. In ourGalaxy, the column densities of OH in diffuse clouds are of the order of$N$(OH)$\sim$10$^{13-14}$ cm$^{-2}$. From the incidence (number per unitredshift; $n_{21}$) of HI 21-cm absorbers at $0.5<z<1$ and assuming no redshiftevolution, we estimate the incidence of OH absorbers (with log$N$(OH)$>$13.6)to be $n_{\rm OH}$ = $0.008^{+0.018}_{-0.008}$ at $z\sim0.1$. Based on this weexpect to detect 10$^{+20}_{-10}$ such OH absorbers from the MeerKAT AbsorptionLine Survey. Using HI 21-cm and OH 1667 MHz absorption lines detected towardsQ0248+430, we estimate ($\Delta F/F$) = (5.2$\pm$4.5)$\times 10^{-6}$, where $F\equiv g_p (\alpha^2/\mu)^{1.57}$, $\alpha$ $-$ the fine structure constant,$\mu$ $-$ the electron-proton mass ratio and $g_p$ $-$ the proton gyromagneticratio. This corresponds to $\Delta\alpha/\alpha$($z=0.0519$) = (1.7 $\pm$1.4)$\times 10^{-6}$, which is among the stringent constraints on thefractional variation of $\alpha$.

Discovery of OH absorption from a galaxy at z~0.05: implications for large surveys with SKA pathfinders