ISO/TR 20811:2017描述了空间和真空应用中激光诱导分子污染（LIMC）研究的设置、测试程序和测量数据分析。 LIMC是由于强光辐射与脱气分子（尤其是来自有机材料的脱气分子）的相互作用而在光学表面上形成沉积物。它是一种分子污染的现象，并且它不同于颗粒污染，颗粒污染可以在光学部件的制造、组装、集成或测试期间发生。 激光诱导沉积的形成会导致光学系统性能的劣化。LIMC可以增加相位失真、散射和吸收。如果激光系统在真空中以短波长和短脉冲持续时间操作，LIMC是特别相关的。在这种情况下，即使在10？5百帕可能对光学性能产生强烈的负面影响。还表明，如果涉及激光诱导沉积，激光诱导损伤阈值可以降低10倍或更多。 在具有额外分子污染的LIMC的情况下，激光诱导的分子污染和激光诱导的损伤都是激光辐射与光学表面的相互作用起主要作用的现象。因此，ISO/TR 20811:2017与ISO 21254（所有部分）相关，ISO 21254规定了确定激光诱导损伤阈值的测试方法。 该方法旨在定性评估所研究的材料是否会在低-存在波长为355 nm的高能纳秒脉冲激光照射的压力环境。由于光化学表面反应的性质，该结果不能直接转移到照射性质被改变的情况（特别是波长、重复率、脉冲持续时间等）。）.由于激光诱导的污染及其检测方法的非线性增长，该技术不提供评估沉积物的定量手段，因此，应将其视为相对于材料的激光诱导的污染行为进行比较的手段。 此外，选择代表性数量的污染材料——代表真实激光系统中存在于光学表面附近的材料分压——超出了该方法的范围。这是用其他方法仔细推导出来的，是在应用此方法之前必须固定的强制性参数。

ISO/TR 20811:2017 describes the setup, test procedure and analysis of measured data for investigation of laser-induced molecular contamination (LIMC) for space and vacuum applications.

LIMC is the formation of depositions on optical surfaces due to interaction of intense light radiation with outgassing molecules especially from organic materials. It is a phenomenon of molecular contamination and it is distinguished from particle contamination, which can occur during manufacturing, assembly, integration or test of the optical components.

Formation of laser-induced depositions can lead to deterioration of the performance of an optical system. Phase distortion, scattering and absorption can be increased by LIMC. LIMC is of particular relevance, if a laser system is operated in vacuum at short wavelength and short pulse duration. In such a case, even small partial pressure of contamination material in the range of 10^？5 hPa could have strong negative impact on optical performance. It was also shown that the laser-induced damage threshold could be reduced by a factor of 10 and more if laser-induced depositions are involved.

Laser-induced molecular contamination and laser-induced damage are both phenomena, for which the interaction of laser radiation with optical surfaces plays a major role, in case of LIMC with additional molecular contamination. Therefore, ISO/TR 20811:2017 is treated in relation to ISO 21254 (all parts) which specifies the test methods for the determination of laser-induced damage thresholds.

This method was derived to evaluate qualitatively, whether the material under investigation causes deposits on optical surfaces in a low-pressure environment in the presence of high-energy nanosecond pulsed laser irradiation at a wavelength of 355 nm. Due to the nature of photochemical surface reactions, this result cannot be directly transferred to scenarios where the properties of the irradiation are altered (especially wavelength, repetition rate, pulse duration, etc.). Due to the non-linear growth of the laser-induced contamination and its detection methods, this technique does not provide quantitative means to evaluate the deposit and, therefore, it should be seen as a means to compare materials relatively with respect to their laser-induced contamination behaviour.

Furthermore, it is out of the scope of this method to select representative quantities of contamination materials - representative with respect to the material partial pressure present in the vicinity of the optical surface in a real laser system. This is carefully derived with other methods and is a mandatory parameter to be fixed before applying this method.