We developed a long-range multipass gas cell that extends the beam path to 18.61 m, for which a THz beam shows multiple reflections within a diameter of only 32 cm and a height of 54 cm. Due to the very long propagation THz beam path in the multipass gas cell, the absorbance and absorption coefficients of nitrous oxide can be measured very sensitively from 0.2 to 1.2 THz bandwidth. The gas concentration can be determined from the measured THz pulses for the absorption. As the gas concentration increased sequentially from 1.0% to 8.3% at atmospheric pressure, the absorbance lines also increased sequentially. The resulting absorptions and frequencies of transitions showed good agreement between experiment and calculations performed with the HITRAN database.

中文翻译：

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使用远程多通道气室对低浓度 N$_2$O 进行太赫兹时域光谱分析

我们开发了一种远程多通道气室，将光束路径扩展到 18.61 m，为此，太赫兹光束在直径仅为 32 厘米、高度为 54 厘米的范围内显示出多次反射。由于多通道气室中传播的太赫兹光束路径非常长，因此可以在 0.2 至 1.2 太赫兹带宽范围内非常灵敏地测量一氧化二氮的吸光度和吸收系数。气体浓度可以从用于吸收的测量的太赫兹脉冲中确定。随着大气压下气体浓度从 1.0% 依次增加到 8.3%，吸光度线也依次增加。由此产生的吸收和跃迁频率在实验和使用 HITRAN 数据库执行的计算之间显示出良好的一致性。