Lower frequency region mid-infrared spectroscopy by chirped pulse upconversion Jingyi Zhu, Tilo Mathes, Andreas D. Stahl, John T.M. Kennis and Marie Louise Groot* EPJ Web of Conferences, 41 (2013) 09004 Published online: 13 March 2013 DOI: 10.1051/epjconf/20134109004