Trans-1,3-Pentadiene spectra is recorded in the 5000-17500 cm(-1) region with conventional and intracavity laser photoacoustic spectroscopy. It can be determined by the spectrophotometric method based on the Diels-Alder reaction. In this reaction, cisoid 1,3-dienes and tetracyanoethylene (TCNE) react with an aromatic-TCNE pi-complex.