darkhistory.physics.coll_exc_xsec

darkhistory.physics.coll_exc_xsec(eng, species=None, method='old', state=None)

e-H or e-He collisional excitation cross section in cm².

see under method for references

Parameters:

eng : float or ndarray

Abscissa of kinetic energies.

species : {‘HI’, ‘HeI’, ‘HeII’}

Species of interest.

method : {‘old’, ‘MEDEA’, ‘AcharyaKhatri’, ‘new’/’eff’}

if method == ‘old’, see 0906.1197; if method == ‘MEDEA’,

see Mon. Not. R. Astron. Soc. 422, 420–433 (2012);

if method == ‘AcharyaKhatri’

see arXiv:1910.06272;

if method == ‘new’,

For np states and HeI, use Kim, Rudd, and Desclaux below 3 keV; between 3 and 10 keV, use nonrelativistic Bethe approximation. For np states above 10 keV, use relativisitics Bethe approximation. For states in {2s, 3s, 3d, 4s, 4d, 4f}, use CCC data below 999 eV; above this energy, use nonrelativistic Bethe expression for < 10 keV and relativistic expression above 10 keV.

if method == ‘eff’, same as ‘new’.

state : str

The excited state (option for methods other than ‘old’)

Returns:

float or ndarray

e-H or e-He collisional excitation cross section.