;+
; NAME:
;  ch4latentheat
; PURPOSE: (one line)
;  Return latent heat of sublimation of CH4 in erg/g from Brown & Ziegler 1980
; CATEGORY:
;  Volatile Transport
; CALLING SEQUENCE:
;  latentheat = ch4latentheat(t)
; INPUTS:
;  t : temperature, K
; KEYWORD INPUTS
;  None
; OUTPUTS:
;  latentheat : latent heat of sublimation in erg/g
; OPTIONAL OUTPUT
;  None
; RESTRICTIONS:
; PROCEDURE:
;  This function implements the tables of Brown and Zeigler 
; MODIFICATION HISTORY:
;  Written 2011 Apr 10, by Leslie Young, SwRI
;-
function ch4latentheat, t

physconstants
if isarray(t) then begin
   l = 0. * t
   for i = 0, n_elements(l)-1 do l[i] = ch4latentheat(t[i])
   return, l
endif

a=[1.71271658e1, -1.11039009e3, -4.34060967e3, 1.03503576e5, -7.91001903e5]

l = -total( (findgen(4)+1) * t^(- (findgen(4)) ) * a[1:4]) * !phys.k / (28.0061 * !phys.m_u)

return, l

end