pro physconstants

;+
; NAME:
;  physconstants
; PURPOSE: (one line)
;   Add a structure of physical constants as a non-standard system variable
; DESCRIPTION:
;  This is just a simple way to collect the physical constants (cgs) together.
;   1998 CODATA recommended values
;   The new set of recommended values is available on the World Wide Web at 
;   physics.nist.gov/constants.
;                              
;   Journal of Physical and Chemical Reference Data, Vol. 28, No. 6, 1999 and in the 
;   Reviews of Modern Physics, Vol. 72, No. 2, 2000. 
;   CODATA Recommended Values of the Fundamental Physical Constants: 1998
;   Peter J. Mohr and Barry N. Taylor
;
; CATEGORY:
;  Astronomy
; CALLING SEQUENCE:
;  physconstants
; INPUTS:
;  none
; OPTIONAL INPUT PARAMETERS:
;  none
; KEYWORD INPUT PARAMETERS:
;  none
; KEYWORD OUTPUT PARAMETERS:
;  none
; OUTPUTS:
;  None.
; COMMON BLOCKS:
;  None.
; SIDE EFFECTS:
;  Defines the system variable !phys using defsysv
; RESTRICTIONS:
; PROCEDURE:
; MODIFICATION HISTORY:
;  Written 2000 April, by Leslie Young, SwRI
;  Added to "layoung" library 2000 October, by Leslie Young, SwRI
;  2004 Apr 5 move to CODATA 2002, added sigma, added some units,
;   fixed sign error in exponent for eV.  LAY SwRI
;  2006 Apr 28.  Make constants doubles.  LAY
;-

on_error, 2

; Don't add it if it already exists.
DEFSYSV, '!phys', EXISTS = i
IF i EQ 1 THEN return

defsysv, '!phys', $
  { $
source: '2002 CODATA values', $
system: 'cgs', $
m_u_name: 'atomic mass constant',  m_u: 1.66053886d-24, m_u_unit: 'g',$
N_a_name: 'Avogadro constant',     N_a: 6.0221415d23,  N_a_unit: 'mol^-1',$
k_name:   'Boltzmann constant',    k:   1.3806505d-16,  k_unit:   'erg K^-1', $
me_name:  'electron mass',         m_e: 9.1093826d-28, m_e_unit: 'g', $
eV_name:  'electron volt',         eV:  1.60217653d-12, eV_unit: 'erg', $
c_name:   'speed of light',        c:   2.99792458d10, c_unit: 'cm s^-1', $
h_name:   'Plank constant',        h:   6.6260693d-27, h_unit: 'erg s', $
sigma_name: 'Stefan-Boltzmann constant', $
    sigma:  5.670400e-5, sigma_unit: 'erg cm^-2 K^-4 s^-1', $
G_name:   'gravitational constant',G:   6.6742e-8 $
  }, 1

message, $
  'Physical constants system variable (!phys) have been added', /inf

end