Specifying specific isotopes with LANL2DZ or other ECP basissets

[eric breynaert <eric.breynaert!at!agr.kuleuven.ac.be>]

 Hello all,
I'm  doing some dft calculations on 99Tc compounds in Gaussian 03
 using
 UB3LYP/LANL2DZ.
 I was wondering how one deals with different isotopes when using an ECP
 basisset. Browsing through the gaussian logfile i found that g03 uses
 atomic weigths 12.0000000, 15.9949146 and 1.0078250 for C,O and H
 respectively. while it uses .0000000 for Tc. Is it possible to specify
 the
 atomic weight for the Tc isotope i'm trying to model, and would this
 have
 an effect on the calculations ?
 Thanks,
 Eric
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