MODULE constants
!
!   Define some constants
!
  INTEGER, PARAMETER       :: dprequestedprec = 15
  INTEGER, PARAMETER       :: db     = SELECTED_REAL_KIND(dprequestedprec)
!
  REAL(kind=db), PARAMETER :: vlight = 299792458.0_db         ! c
  REAL(kind=db), PARAMETER :: vacimp = 376.73031346177066_db  ! \mu_0*c
  REAL(kind=db), PARAMETER :: eev    = 510998.89613320108_db  ! m_e*c^2/e
  REAL(kind=db), PARAMETER :: me     = 9.109383E-31           ! electron mass [kg]
  REAL(kind=db), PARAMETER :: pi     = 3.1415926535897931_db
  REAL(kind=db), PARAMETER :: elchar = 1.60217662E-19_db      ! electron charge [C]
  REAL(kind=db), PARAMETER :: eps_0  = 8.85418781762E-12_db   ! electric constant [F/m]
  REAL(kind=db), PARAMETER :: kb     = 1.38064852E-23_db      ! Boltzman constant [J/K]
END MODULE constants