T=1.00 us
T=4.00 us
T=7.00 us
T=10.0 us
T=13.0 us
T=16.0 us
T=19.0 us
T=22.0 us
T=25.0 us
T=28.0 us
T=31.0 us
T=34.0 us
"Measurements of Symmetric Vortex Merger", K.S. Fine, C.F. Driscoll, J.H.Malmberg and T.B. Mitchell; Physical Review Letters vol 67, pg 588 (1991).