Symes Rachel, Gilham Richard J J, Sayer Robert M, Reid Jonathan P
School of Chemistry, University of Birmingham, Edgbaston, Birmingham, UK B15 2TT.
Phys Chem Chem Phys. 2005 Apr 7;7(7):1414-22. doi: 10.1039/b500385g.
Stimulated Raman scattering (SRS) from single aerosol droplets can be observed at extremely low laser threshold intensities at wavelengths commensurate with whispering gallery modes. Although droplet size can routinely be determined from the ensuing cavity enhanced Raman scattering (CERS) fingerprint, determining droplet composition is a considerably more challenging measurement. We present here an examination of the factors that influence and limit the detection sensitivity of CERS in quantifying the concentrations of sulfate and nitrate in water droplets, 20-50 microm in radius. In particular, we consider the variation in nitrate and sulfate SRS signal with variation in species concentration, probe laser intensity and droplet size. We illustrate that the band contour of the OH stretching band can be used as a relative measure of the internal light intensity circulating within the droplet and experimentally investigate how the threshold condition for SRS is achieved.
在与回音壁模式相当的波长下，在极低的激光阈值强度下即可观察到单个气溶胶液滴的受激拉曼散射（SRS）。虽然通常可以从随后的腔增强拉曼散射（CERS）指纹图谱中确定液滴大小，但确定液滴成分是一项更具挑战性的测量。我们在此研究了影响和限制CERS检测灵敏度的因素，该检测用于量化半径为20 - 50微米的水滴中硫酸盐和硝酸盐的浓度。特别是，我们考虑了硝酸盐和硫酸盐SRS信号随物种浓度、探测激光强度和液滴大小变化的情况。我们表明，OH伸缩带的能带轮廓可作为液滴内循环光强的相对度量，并通过实验研究如何实现SRS的阈值条件。
