c     constants

      double precision pi, m_n, h_blanck
      parameter	(pi		= 3.14159,
     +		 m_n            = 0.1045407751,	! meV/(Angstrom/psec)^2
     +		 h_blanck       = 4.13570)	! meV*psec
c
      double precision gy
      parameter(gy     =18.324718d-12)          ! 1/(mGaus*psec)