If laser beams of {HEAD ~ a predetermined wavelength} are irradiated, electrons are excited beyond the forbidden band by {TAIL ~ optical energy} in the semiconductor electrode of the hydrogen producing unit 
If laser beams of { HEAD ~ a predetermined wavelength } are irradiated , electrons are excited beyond the forbidden band by { TAIL ~ optical energy } in the semiconductor electrode of the hydrogen producing unit
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH