c     constants

      double precision pi, m_n, h_par, k_b, avog
      double precision he4mol, gam, rgas
      parameter	(pi		= 3.14159,
     +		 m_n            = 0.1045407751,	! meV/(Angstrom/psec)^2
     +		 h_par          = 0.6582122,	! meV*psec
     +		 k_b            = 0.08617,      ! Boltzman const (meV/K)
     +		 avog		= 0.6022,       ! Avodadro's no. (10^24 atom/mol)
     +		 he4mol		= 4.0,		! helium4 (gm/mol)
     +		 gam		= 1.6666666667,	! adiabatic const
     +		 rgas		= 8.314)	! gas constant (J/mol*K)

      double precision gy, mag_b
      parameter(gy     =18.324718,   ! 1/(mGaus*sec)
     +		mag_b  = 0.1)       ! mGaus
      double precision k_0, bb
      parameter	(k_0   = 0.75,                  ! 1/Ang
     +		 bb    = 3.07729087d-15)        ! scattering length (m)