  The alpha-decay half-lives of recently synthesized superheavy nuclei (SHN)
are investigated based on a unified fission model (UFM) where a new method to
calculate the assault frequency of alpha-emission is used. The excellent
agreement with the experimental data indicates the UFM is a useful tool to
investigate these alpha-decays. It is found that the half-lives become more and
more insensitive to the Q_alpha values as the atomic number increases on the
whole, which is favorable for us to predict the half-lives of SHN. In addition,
a formula is suggested to compute the Q_alpha values for the nuclei with Z > 92
and N > 140 with a good accuracy, according to which the long-lived SHN should
be neutron rich. With Q_alpha values from this formula as inputs, we predict
the half-lives of isotopes of Z = 117, which may be useful for experimental
identication in the future.
