Dubnium Ionization Energy

The Dubnium Ionization Energy is the energy required to remove from atom one mole of electrons with subsequent production of positively charged ion of Dubnium.
Db -> Db⁺ + e^-
This process can be repeated many times, but the energy cost is increased dramatically. The general equation for the Dubnium is:
Db^N+ -> Db^(N+1)+ + e^-

There is no data about Dubnium ionization energy