A novel multipass photoacoustic cell with five stacked electromechanical films as a microphone has been constructed, tested and characterized. The photoacoustic cell is an open rectangular structure with two steel plates facing each other. The longitudinal acoustic resonances are excited transversely in an optical multipass configuration. A detection limit of 22 ppb (10−9) was achieved for flowing NO2 in N2 at normal pressure by using the maximum of 70 laser beams between the resonator plates. The corresponding minimum detectable absorption and the normalized noise-equivalent absorption coefficients were 2.2 × 10−7 cm−1 and 3.2 × 10−9 cm−1WHz−1/2, respectively.
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机译：具有五个堆叠的机电薄膜作为传声器的新型多通道光声单元已被构建，测试和表征。光声电池是具有两个彼此面对的钢板的开放矩形结构。纵向声共振在光学多程配置中被横向激发。通过在共振板之间使用最多70束激光束，在常压下使N2中的NO2流动时，检测极限达到22 ppb（10 -9 ）。相应的最小可检测吸收和归一化噪声等效吸收系数为2.2×10 −7 cm -1 和3.2×10 −9 cm -1 WHz −1/2 。
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