Ionization rate calculation does not use `ioniz_cross` function

[wtbarnes]

ioniz_cross calculates the ionization cross section as a function of energy, using the approach of Dere et al. (2007) or Fontes et al. (1999) depending on the ion,

chianti-idl/ionrec/ioniz_cross.pro

Line 108 in 6641fae

FUNCTION ioniz_cross,gname,energy_in,z=z,ion=ion,verbose=verbose

However, this function is not actually used when calculating the ionization rate in ioniz_rate. Rather, the ionization cross-section is (redundantly) calculated for only the Dere et al. case:

chianti-idl/ionrec/ioniz_rate.pro

Lines 181 to 191 in 6641fae

	x0=double(ev1(ifac)/tev(it))
	beta=sqrt(kb*temperature(it))
	egl=ev1(ifac)+xgl*tev(it)
	scale_bt,egl,dum,dum,btf(ifac),ev1(ifac),btgl,dum,dum
	; di splines were made with a cubic spline fit
	y2=spl_init(x_spline(*,ifac),y_spline(*,ifac))
	btcross=spl_interp(x_spline(*,ifac),y_spline(*,ifac),y2,btgl)
	btcross=double(btcross)
	descale_bt,btgl,btcross,dum,btf(ifac),ev1(ifac),evd2,crossgl,odum
	newcross=alpha*beta*exp(-x0)*(total(wgl*xgl*crossgl)+x0*total(wgl*crossgl))
	dirate(it)=dirate(it)+newcross

ioniz_rate should be refactored to use ioniz_cross such that the Fontes calculations are taken into account and to reduce the redundant implementations of the Dere et al. cross-section calculation.

[pryoung]

The Dere spline fits in the diparams files for H-like and He-like ions were performed to the Fontes data, so the Fontes cross-sections from ioniz_cross should match those computed from ioniz_rate. I'm not sure why he treated Fontes differently in ioniz_cross, but I don't believe this routine is used anywhere else in CHIANTI. In fact it might be best to move it to the obsolete branch.

[wtbarnes]

Thanks! I was not aware of that. Yes, as far as I can tell it is not used anywhere else.