This in turn sets constraints on A at certain frequencies, e.g., where O-H absorptions or overtone-combination modes occur in the NIR.
This common structural trait shared between ordered and disordered PBTTT chains localizes excitations, hence, the invariance of Raman overtone-combination intensities with PCBM loading.
Prior optical noninvasive in vivo glucose detection studies have been focused on the near-infrared (near-IR) [ 4] due to the presence of resonant glucose overtone and combination bands combined with low water absorption in that region, which allows for greater penetration of light into skin.
Owing to the anharmonicity of the molecular vibrations, transitions corresponding to multiples (2νi, 3νi, etc, known as overtones) and combinations (ν1 + ν2, 2ν3 + ν4, etc). of the fundamental frequencies will occur.
NIR spectra contain fewer specific spectral features than mid-IR, as overtone and combination bands overlap, making band assignment challenging.
In particular, the observed NIR emissions are well overlapped with the vibrational absorption (overtone and combination) bands of water molecule (Carleer et al. 1999).
The direct interpretation of measured NIR spectra is complicated by overlapping bands produced from overtone and combination bands of chemical bonds.
In particular, we show that both overtone and combination modes have essential contribution to the 2D band, bringing about specific modifications of the band shape.
We present complete calculations of the two-phonon Raman bands of bilayer graphene, including all overtone and combination modes, within a density-functional tight-binding model.
For the three electrodes examined, the overtone and/or combination bands, due to vertically oriented hydrogen terephthalate, were observed at 2642 and 2517 cm−1, respectively.
