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 C2H4 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 × 10−26 cm2/mol, equivalent to ≅0.05km−1/amagat. The self-broadening coefficient has been measured for one of the most intense lines.

► In this spectroscopic work new ethylene absorption lines have been observed at 830 nm. ► Laser diodes sources and the frequency modulation technique permit fine spectroscopy. ► Absorption Cross Sections as low as 2×10−26 cm2/mol have been detected. ► These results can be important also from the astrophysical view point.