= Ian Czekala
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<Ian Czekala> teaches a physical account of heating and cooling in <H II regions>. His nebular <energy> balance distinguishes the energy spent removing an <electron> from an <atom> from the excess <photon> <energy> that becomes <electron> <kinetic energy>.
In the lecture's account, <photoionization> supplies heating, while <radiative recombination> and collisional excitation followed by photon emission remove thermal <energy>. Balancing these processes determines the <gas> <temperature>. This explains why neither the ionization threshold nor the typical photon energy alone specifies the equilibrium <temperature>.<Heating and Cooling of HII regions by Ian Czekala>[Opening physical overview and Heating by photoionization: excess energy and competing losses]{ref}
\Image[https://iancze.github.io/people/Ian_Czekala_hu_32731f20fce55d69.jpeg]
{title=Portrait of <Ian Czekala>}
{description=External portrait linked from the identified institutional or researcher profile.}
{source=https://iancze.github.io/people/}
{width=240}
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