•
 •Energy absorbed/emitted depends on upper and
 lower levels
 •Higher energy levels are close together
 •Above a certain energy, electron can
 escape    
 (ionization)
 •
 •Series of lines named for bottom level
 –To get absorption, lower level must be
 occupied
 •Depends upon temperature of atoms
 –To get emission, upper level must be
 occupied
 •Can get down-ward cascade through many
 levels
 •
 •