identidication problem in nl estrimation (STATA)

Dear All:

I am trying to estimate the parapétters in the equation spccifyed in the file attached. Since it is quite non-liner, we have tryed non-linear least squares and even GMM (taking all terms to the left hand side and making it all equal cero). Non of them works. Do you have any suggesting as to how to estimate this model ?.

Many thanks in advance: Leonardo Letelier S.