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