  The precise measurement of molecular vibrational transition frequencies is
useful in the search for variation in the proton-to-electron mass ratio {\mu}.
Homonuclear diatomic molecules are particularly advantageous for precise
measurement because of the small Stark shift. This paper discusses the Stark
and Zeeman shifts in the 16O2+ vibrational transition frequencies.To search for
the variation {\mu}(<10-17/yr), the X2{\Pi}1/2(v,J)=(0,1/2)-(v',1/2)(v'>1)in
transition frequencies are much more advantageous than the transition
frequencies between the X2{\Pi}1/2 v=21 and a4{\Pi}1/2 v=0 states, whose
sensitivity to the variation in {\mu} is high because of the accidental
degeneracy.
