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tokens: ) assigned both peaks to transpolyacetylene at grain boundaries and surfaces of nanodiamonds. The weak peak at ∼1020 cm −1 along with the broad feature centered at ∼1270 cm −1 are also associated with nanodiamonds (Veres et al. 2007 ; May et al. 2008 ), and the broad doublet at ∼1800 and 1900 cm −1 may be due to overtones and/or combinations. In the 2000–4000 cm −1 region (not shown), the Raman spectra show broad CH-stretching peaks centered at ∼2900 cm −1 in addition to the second-order peaks of nanodiamonds and graphitic/amorphous carbon. Figure 2. Reflected-light image from the KBr pellet of the Kapoeta carbonaceous-chondrite material showing a cluster of diamond particles. Figure 3. Raman spectra of the Kapoeta nanodiamonds (see the text for details). Thus, in the cluster of particles shown in Figure 2 , each particle may be considered as an aggregate of nanodiamonds. To estimate the sizes of these nanodiamonds from their Raman spectra, we consider the particle-size dependence of the position and FWHM of the 1333 cm −1 diamond peak (Yoshikawa et al. 1993 ). Based on the analyses of 26 Raman spectra, the average diamond peak position and FWHM are 1332.6 cm −1 ( σ = 0.3 cm −1 ) and 4.0 cm −1 ( σ = 0.6 cm −1 ), respectively, suggesting a particle size of ≥50 nm for the Kapoeta diamonds that show the Raman diamond peak in their spectra. However, some spectra do not show the Raman diamond peak at 1333 cm −1 , but they display all the other peaks shown in Figure 3 (a), including the peaks and features associated with nanodiamonds at ∼1020, 1150, 1450 cm −1 , and ∼1270 cm −1 (Figure 3 (b)). The spectrum shown in Figure 3 (b) is very similar to the Raman spectra of ultrananocrystalline diamonds having an average particle size of ∼3–5 nm, i.e., single-digit nanodiamonds, where the 1333 cm −1 diamond peak is absent and they show the D- and G-bands along with the 1150 and 1450 cm −1 peaks (Popov et al. 2004 ). One difference is that the G-band in their spectra occur at a lower wavenumber (1560 cm −1 ), possibly due to differences in sp 2 /sp 3 ratios in the amorphous carbon phase. Thus, our Raman spectroscopic data suggest the existence of two populations of nanodiamonds in the Kapoeta CC material: nanodiamonds that are ≥50 nm and single-digit nanodiamonds. 3.3. Micro-FTIR Spectroscopy Figure 4 (a) shows a typical micro-FTIR spectrum taken from the diamond-enriched region (spot size is ∼70 μ m). It is dramatically different from the KBr-pellet spectrum (Figure 1 ) both in the high- and low-frequency sides. The position of the absorption bands and their possible assignments are listed in Table 1 . Figure 4. (a) Micro-FTIR spectrum collected from the diamond-enriched region in the KBr pellet of the Kapoeta carbonaceous-chondrite material (see the text for details). (b) Expanded view of the C–H stretch region. Table 1 Assignment of IR Bands in FTIR Spectrum of the Diamond-enriched Region of the Kapoeta CC Material 3.3.1. C–H Stretching Bands The C–H