Nuclear acoustic resonance in single-crystal hydrogen-free tantalum

Nuclear-acoustic-resonance studies have been made of single-crystal 99.99% pure tantalum metal from which all hydrogen has been removed (hydrogen concentration much less than 7 at. ppm or 0.04 wt ppm). The shapes and widths of the 181Ta Δm = plus-or-minus1 and plus-or-minus 2 absorption lines can be explained as due to quadrupole broadening caused by a random distribution of charged impurities. Unlike hydrogenated Ta, the Δm = plus-or-minus 2 line shape and linewidth for the hydrogen-free specimen are independent of magnet angle and temperature between 78 and 300 K. The measured 181Ta Knight shift is (1.14 plus-or-minus 0.02) % relative to 181Ta in KTaO3. The magnitudes and relative signs of the components of the tensor relating electric field gradient to elastic strain are S11 = plus-or-minus 26 times 1015 statcoulomb cm-3 and S44 = minus-or-plus 29 times 1015 statcoulomb cm-3