An effort over several months in the Chen laboratory to reproduce the spectra in our previous work1 has not produced usable data. We have also received preliminary but convincing data from Prof. Michael Duncan, University of Georgia, that differ substantially from ours. We therefore wish to retract our paper.

1.
T.
Gilbert
,
R.
Pfab
,
I.
Fischer
, and
P.
Chen
,
J. Chem. Phys.
112
,
2575
(
2000
).