The vibration-rotation spectrum of the perpendicular band nu(7) of (Si
2F6)-Si-28,28 has been studied in a supersonic free jet with 0.001 cm(
-1) resolution. The spectrum covering the K Delta K = -17 to 8 subband
s shows a local perturbation for K Delta K > 2. The whole spectrum has
been successfully analyzed by assuming a Fermi interaction from a ver
y close combination state. Also. the Q branch of the nu(7) band of (Si
2F6)-Si-28,29 has been identified. (C) 1995 Academic Press, Inc.