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Incoherent broad band cavity enhanced absorption spectroscopy (IBBCEAS),〔Fiedler, S. E.; Hese, A. and Ruth, A. A. ''Incoherent broad-band cavity-enhanced absorption spectroscopy'', Chem. Phys. Lett. 2003, 371, 284.〕 sometimes called broadband cavity enhanced extinction spectroscopy (IBBCEES), measures the transmission of light intensity through a stable optical cavity consisting of high reflectance mirrors(typically R>99.9%). The technique is realized using incoherent sources of radiation e.g. Xenon arc lamps, LEDs or supercontinuum (SC) lasers, hence the name. Typically in IBBCEAS, the wavelength selection of the transmitted light takes place after the cavity by either dispersive or interferometric means. The light is either directly focused onto the entrance slit of a monochromator and imaged onto a charged coupled device (CCD) array via a dispersive optical element (e.g. a reflection grating) or imaged onto the entrance aperture of a conventional interferometer. The spectrum is reconstructed taking the Fourier transform of the recorded interferogram. Similar to other cavity enhanced spectroscopic techniques, in IBBCEAS, the transmission signal strength is measured with and without the absorber of interest present inside the cavity ( ''I(λ)'' and ''I0(λ)'' respectively). From the ratio of the wavelength-dependent transmitted intensities, the effective reflectivity of the mirrors ''Reff(λ)'' and the sample path length per pass ''d'' inside the cavity, the sample's extinction coefficient ''α(λ)'' is calculated as: : The sensitivity (smallest achievable α for a given sample) increases for large mirror reflectivities and large path lengths in the cavity, which is maximal, if ''d'' equals the cavity length.(1-Reff) includes all unspecified losses per pass (e.g. scattering or diffraction losses) other than the losses due to the limited reflectivity of the cavity mirrors. Note that although the technique is often used for studying absorption, total light extinction, ''α'', is retrieved, and it therefore measures the sum of absorption and scattering. The advantages of IBBCEAS include: * 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Incoherent broad-band cavity-enhanced absorption spectroscopy」の詳細全文を読む スポンサード リンク
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