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The roadblock on the way to perform the quantum mechanical calculation as the "SCF or DFT" method for some molecules such as drugs, biological molecules, and so on is that these molecules are too large to study. They need a computer with a large amount of system memory and a very fast CPU. Therefore, we are looking for an entirely quantum-mechanical procedure to study the electronic properties of a large molecule with considerable saving computational time and acceptable accuracy. This procedure is based on searching for the active parts of a molecule, which are essentially HOMO and LUMO parts and their surroundings, and is called truncated molecule (TM) in this manuscript. To this end, at first, this procedure is inspected for Mn-complex, due to the availability of its experimental UV spectra. The calculation of the UV spectrum for TM part of Mn-complex shows λmax = 355.64 nm, while experimental UV spectra is λmax = 334.31 nm, and the corresponding theoretical value for the original molecule reveals λmax = 346.99 nm. The CPU time for the original molecule is 448,045 s that is reduced to 101,555 s for TM with acceptable accuracy (the CPU ratio is 4.41). Furthermore, this procedure is also tested for one of the sequences of A-chain of insulin, Docetaxel (drug molecule), and Taxol (drug molecule); the acceptable resemblance between UV spectra of the original and TM molecule is obtained. The computational time is reduced with a ratio of 3.59, 2.44, and 1.69, respectively. [ABSTRACT FROM AUTHOR]

A generalization of the Raman scattering (RS) spectrum, the Raman excitation map (REM) is a hyperspectral two-dimensional (2D) data set encoding vibrational spectra, electronic spectra and their coupling. Despite the great potential of REM for optical sensing and characterization with remarkable sensitivity and selectivity, the difficulty of obtaining maps and the length of time required to acquire them has been practically limiting. Here we show, with a simple setup using current optical equipment, that maps can be obtained much more rapidly than before (~ms to ~100 s now vs. ~1000 s to hours before) over a broad excitation range (here ~100 nm is demonstrated, with larger ranges straightforward to obtain), thus taking better advantage of scattering resonance. We obtain maps from different forms of carbon: graphite, graphene, purified single walled carbon nanotubes (SWCNTs) and chirality enriched SWCNTs. The relative speed and simplicity of the technique make REM a practical and sensitive tool for chemical analysis and materials characterization. [ABSTRACT FROM AUTHOR]