Schendel J S, Stickel R E, Vandijk C A, Sandholm S T, Davis D D, Bradshaw J D
Appl Opt. 1990 Nov 20;29(33):4924-37. doi: 10.1364/AO.29.004924.
Vacuum ultraviolet/photofragmentation laser-induced fluorescence has been demonstrated to be a highly specific and sensitive method for the quantitative measurement of atmospheric ammonia (NH(3)). The fluorescence detected in this approach results from the two 193-nm photon photofragmentation step NH(3)?NH(2)? NH(b(1)Sigma(+)) followed by the excitation of the NH(b(1)Sigma(+)) NH(c(1)Pi) transition via a 450-nm photon with final emission being observed from the NH(c(1) Pi) NH(a(1)Delta) transition at 325 nm. Limits of detection for the instrumentpresented here are < 10 pptv and < 4 pptv for 1- and 5-min integration periods, respectively, in ambient sampling conditions. The technique is free from interferences and system performance does not significantly degrade in adverse sampling conditions (i.e., rain, fog, clouds, haze, etc.). Spectroscopic selectivity in the NH(b(1)Sigma(+))?NH(c(1)Pi) transition is sufficient to resolve (15)NH(3) and (14)NH(3) contributions for use in atmospheric tracer studies. Average ammonia measurements at Stone Mountain, GA, ranged from approximately 110 pptv for air temperatures <5 degrees C to approximately 240 pptv for air temperatures >/=<5 degrees C over the period from Dec. 1987 to the end of Apr. 1988.
真空紫外/光碎片激光诱导荧光已被证明是一种用于定量测量大气中氨（NH₃）的高度特异性和灵敏的方法。这种方法中检测到的荧光来自于两个193纳米光子的光碎片步骤：NH₃→NH₂→NH（b¹Σ⁺），随后通过一个450纳米光子激发NH（b¹Σ⁺）→NH（c¹Π）跃迁，最终在325纳米处观察到从NH（c¹Π）→NH（a¹Δ）跃迁的发射。在此展示的仪器在环境采样条件下，1分钟和5分钟积分时间的检测限分别小于10皮克/升和小于4皮克/升。该技术不受干扰，并且在不利的采样条件（即雨、雾、云、霾等）下系统性能不会显著下降。NH（b¹Σ⁺）→NH（c¹Π）跃迁中的光谱选择性足以分辨（¹⁵）NH₃和（¹⁴）NH₃的贡献，用于大气示踪研究。在1987年12月至1988年4月底期间，佐治亚州石山的平均氨测量值范围从气温<5摄氏度时的约110皮克/升到气温≥5摄氏度时的约240皮克/升。
