THz transmittance measurements of nucleobases and related molecules in the 0.4- to 5.8-THz region using a GaP THz wave generator

An automatic measurement system for terahertz (THz) transmission spectroscopy based on difference-frequency generation (DFG) of widely tunable coherent THz waves via excitation of a phonon–polariton mode in GaP was constructed and improved to give it a wider frequency measurement range and four times greater S/N ratio by using the double-beam method. In this paper, we present spectroscopic measurements of nucleobases, nucleosides, deoxynucleosides, and nucleotides, all of which are the components of RNA and DNA molecules, in the range of 0.4–5.8 THz in order to compare their characteristic features in the wider terahertz frequency region. 2004 Elsevier B.V. All rights reserved. PACS: 07.57. c; 42.65.Hw; 63.20.Dj; 87.64. t