Depth selective CEMS

Conversion electron Mossbauer spectroscopy (CEMS) measurements with back scattering geometry have the merit that spectra can be obtained from a sample with much less isotope content compared with transmission measurements. Another merit is that a sample, deposited on a thick substrate, could be measured, and that because of the limited escape depth of the conversion electrons, depth-selective surface studies are possible. The CEMS technique was found to be best applicable to specimens of 10-100 pg Au cm, i.e., about two orders of magnitudes thinner than required for measurements in transmission mode [443]. This way (1) very thin films of gold alloys, as well as laser- and in beam-modified surfaces in the submicrometers range of depth [443], and (2) metallic gold precipitates in implanted MgO crystals [444] were investigated. 

The glass chip used for the same-single-ceU analysis was fabricated by the standard microfabrication procedure, with the channel depth of 20 pm (Fig. 3) [21]. This microfluidic chip was applied for analysis of human wild-type (WT) T-ceU leukemic cell line CCRF-CEM (CEMAVT, dmg sensitive) and its multidrug-resistant vinblastine-selected subline (CEMA LBO.05) [5, 21]. 

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