Diode laser spectroscopy of ethylene overtones at 830 nm

A tunable diode laser spectrometer has been employed to examine the 3rd overtone absorption lines of C(2)H(4) at around 12 000 cm(-1) (830 nm). The spectrometer sources are heterostructure AlGaAs tunable diode lasers operating "free-running". By the aid of the wavelength modulation spectroscopy with the second harmonic detection technique and a Herriott type multipass cell 63 very weak absorption lines have been observed for the first time, with cross sections as low as 2 x 10(-26) cm(2)/mol, equivalent to congruent to 0.05 km(-1) /amagat. The self-broadening coefficient has been measured for one of the most intense lines. (C) 2011 Elsevier Ltd. All rights reserved.