Searches for B0 Decays to Combinations of Two Charmless Isoscalar Mesons

We search for B meson decays into two-body combinations of {eta}, {eta}{prime}, {omega}, and {phi} mesons from 89 million B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We find the branching fraction {Beta}(B{sup 0} {yields} {eta}{omega}) = (4.0{sub -1.2}{sup +1.3} {+-} 0.4) x 10{sup -6} with a significance of 4.3 {sigma}. For the other decay modes we set the following 90% confidence level upper limits on the branching fractions, in units of 10{sup -6}: {Beta}(B{sup 0} {yields} {eta}{eta}) < 2.8 {Beta}(B{sup 0} {yields} {eta}{eta}{prime}) < 4.6, {Beta} (B{sup 0} {yields} {eta}{prime}{eta}{prime}) < 10, {Beta}(B{sup 0} {yields} {eta}{prime}{omega}) < 2.8, {Beta} (B{sup 0} {yields} {eta}{phi}) < 1.0, {Beta} (B{sup 0} {yields} {eta}{prime}{phi}) < 4.5, and {Beta}(B{sup 0} {yields} {phi}{phi}) < 1.5.