  This paper reports measurements using the technique of On Line Nuclear
Orientation (OLNO) which reexamine the gamma decay of isomeric $^{\rm
180}$Hf$^{\rm m}$ and specifically the 501 keV 8$^{\rm -}$ -- 6$^{\rm +}$
transition. The irregular admixture of E2 to M2/E3 multipolarity in this
transition, deduced from the forward-backward asymmetry of its angular
distribution, has for decades stood as the prime evidence for parity mixing in
nuclear states. The experiment, based on ion implantation of the newly
developed mass-separated $^{\rm 180}$Hf$^{\rm m}$ beam at ISOLDE, CERN into an
iron foil maintained at millikelvin temperatures, produces higher degrees of
polarization than were achieved in previous studies of this system. The value
found for the E2/M2 mixing ratio, $\epsilon$ = -0.0324(16)(17), is in close
agreement with the previous published average value $\epsilon$ = - 0.030(2), in
full confirmation of the presence of the irregular E2 admixture in the 501 keV
transition. The temperature dependence of the forward-backward asymmetry has
been measured over a more extended range of nuclear polarization than
previously possible, giving further evidence for parity mixing of the 8$^{\rm
-}$ and 8$^{\rm +}$ levels and the deduced E2/M2 mixing ratio.
