Resumo
A simple, semi-empirical, one-parameter calculation model based on the quantum mechanical tunneling mechanism through a potential barrier has been used to estimate the partial $\alpha$-decay
half-life, $\alphaHL\,$, of $^{178}$Hf$^{\,m2}$ isomer. Alpha-transitions to levels of the ground-state band
$J^{\pi} = 0^{+},\, 2^{+},\, \ldots\, ,\, 14^{+}$ of $^{174}$Yb have been considered, and the contributions to $\alphaHL$ due to overlapping, Coulomb, and centrifugal barriers have been detailed in each case. Results have indicated a
$\alphaHL$-value of $(0.24\pm 0.07)\:$Gyr and a predominance ($\sim 57\,$\%) of $\alpha$-particles populating the level $J^{\pi}= 6^{+},\, E_{\gamma} = 526\:$keV, compatible with results by other authors. Besides, a single, universal-like formula to estimate half-life of alpha transitions, whatever $\ell$-value and the characteristics of the parent nucleus (e-e, e-o, o-e, and o-o nuclei, whether in the ground or isomeric states), has been envisaged.