Differential optoacoustic absorption detector

In a differential optoacoustic absorption detector, the improvement comprising:

• two isolated and tapered gas cells in parallel, each cell having a small diameter at one end and a larger diameter at its opposite end, and a circular cross section of the same diameter at the same point along the length of each cell;
• means for producing a beam of monochromatic light;
• two mirrors, one mirror at the small-diameter end of each cell positioned at 45.degree. with respect to the cell axis to direct light exiting one cell through the other cell;
• a lens for focusing said beam of light from said light-producing means onto a principal focus point between said mirrors half way between said axes of said cells;
• and
• means positioned between said cells for sensing the difference in pressure of gases in said cells while being illuminated by said focused beam of light, whereby gases in said cells are subjected to maximum illumination with a minimum of gas volume.

In a differential optoacoustic absorption detector, the improvmeent comprising:

• two tapered gas cells side by side, each cell having the same cross-sectional area at each point along its length as the other cell, said cells being disposed parallel to each other with one effectively a mirror image of the other;
• means for producing monochromatic light;
• means for directing said monochromatic light through said cells and means for shaping said light passing through each of said cells into a beam conforming to the shape of said cells, whereby essentially all volume of gas in each of said cells is illuminated, said means for directing said monochromatic light through said cells including a beam splitting means for dividing said light into two beams and at least one mirror for directing one of said two beams through one of said cells, and said means for shaing beams is comprised of two lenses, one for shaping a beam through each of said cells of substantially the same shape conforming to the shape of said cells, and
• means for sensing the difference in pressure of gases in said cells while being illuminated by said monochromatic light, said means being positined between said cells for close coupling thereto, whereby gases in said cells are subjected to maximum illumination with aminimum of unilluminated gas.