Highly sensitive and selective measurements of NO2 on HALO

对于发生在空气质量的光化学处理的评估，高灵敏度的活性氮物种的测量是必要的。虽然在德国有几个小组有能力在低ppt范围内测量NO，但仍然缺乏直接测量NO2的能力（在欧洲也是如此）。NO2主要通过转化为NO间接测量。因此，不能完全排除其他含氮化合物也转化为NO引起干扰的可能性。激光诱导荧光（LIF）已经被证明可以直接检测NO2，并且具有高选择性，检测限低至5 ppt/min。最近，二极管激光器已经可以发射蓝光，在NO2吸收最强的波长范围内可调，这将使人们有可能建立一个更紧凑，仍然高度灵敏的LIF仪器来检测NO2。我们已经开发了一个原型，并建议完成一个适合选择性地测量NO2的HALO与所需的灵敏度的仪器的开发。我们已经参与了计划于2011年夏季进行的OMO活动，使用我们的LIF仪器测量OH和HO 2。这里提出的NO2仪器可以集成到我们的HOX LIF中，允许对NO2进行额外的测量，而不会显著增加任何HALO使命的空间，重量和功率要求，其中包括我们的HOX测量。

For the assessment of the photochemical processing that occurs in an air mass, highsensitivity measurements of reactive nitrogen species are a necessity. While in Germany a few groups have the capability to measure NO in the low ppt range, the capability for direct measurements of NO2 with this sensitivity is still missing (also in Europe). NO2 is mostly measured only indirectly via conversion to NO. Hereby the possibility that other nitrogen compounds are also converted to NO causing interferences can never be completely excluded. Laser-induced fluorescence (LIF) has already been demonstrated to detect NO2 directly and with high selectivity, reaching detection limits down to 5 ppt/min. This however required the use of large and expensive laser systems. Recently, diode lasers have become available emitting blue light, tunable in the wavelength range where the NO2 absorption is strongest, which will make it possible to build a much more compact and still highly sensitive LIF instrument to detect NO2. We have already developed a prototype and propose to complete the development of an instrument suitable to selectively measure NO2 on HALO with the required sensitivity. We are already involved in the OMO campaign planned to take place in summer 2011 with our LIF instrument to measure OH and HO2. The instrument for NO2 proposed here can be integrated into our HOX LIF, allowing additional measurements of NO2 without adding significantly to space, weight and power requirements on any HALO mission where our HOX measurements are included.