Far-infrared photoacoustic spectra of tetracene, pentacene, perylene and pyrene

Far-infrared photoacoustic (PA) spectra of four different four- and five-ring aromatic hydrocarbons (tetracene, pentacene, perylene and pyrene) were acquired in this investigation. The use of large-amplitude phase-modulation and step-scan spectrometer operation yielded research-quality PA spectra in the 100-700 cm−1 region. The bands in these spectra were correlated with published infrared and Raman spectra and with calculated band positions. The PA spectra contain many previously unobserved bands and complement the information already obtained from other types of vibrational spectra for the four compounds.