Photoacoustic cell for reflection and transition measurements

A photoacoustic cell is described in which the sample can constitute one of the cell walls. The cell, which can be used alone or in a combined unit with a reference cell, allows nondestructive investigation of a variety of samples either in a normal reflection mode (pressure wave generated at illuminated surface) or in a thermal or elastic transmission mode (pressure wave generated at opposite surface). Simultaneous sample illumination from both sides is possible, too. The cell sensitivity, as measured for an electrically-generated thermal wave, is about 10^-2 V/W at 34 Hz. Use of the cell is illustrated by the dependence of the photoacoustic signal, generated by transmitted thermal and/or elastic waves, on the thickness of copper plates, and by the photoacoustic spectrum resulting from illumination through Begonia leaves.