This lower energy light is produced when electrons decay to or from impurity states between the main energy bands.
(This lower energy light; is produced; T:when electrons decay to or from impurity states between the main energy bands) (electrons; decay; to or from impurity states between the main energy bands)
This lower energy light electrons
is produced decay
T:when electrons decay to or from impurity states between the main energy bands
to or from impurity states between the main energy bands