The absorption of {HEAD ~ the energy} of {TAIL ~ the third laser beam} is also measured using photoacoustic methods 
of
The absorption of { HEAD ~ the energy } of { TAIL ~ the third laser beam } is also measured using photoacoustic methods
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH