High resolution ethylene absorption spectrum between 6035 and 6210 cm-1

A two-channel photo-acoustic spectrometer (PA spectrometer) with a near infrared diode laser was used for taking measurements of a high resolution ethylene absorption spectrum. A semiconductor TEC-100 laser with an outer resonator generates a continuous single-frequency radiation in the range 6030-6300 cm(-1). A newly designed model of photo-acoustic detector (PAD) in the form of a ring type resonator provides for measurement of weak absorption cross-section equal to 4x10(-23) cm(2)/mol at a laser radiation power of 3 mW. The PAD threshold sensitivity is 2x10(-9) cm(-1)Hz(-1/2)W, when the signal to noise ratio equals to 1. The ethylene absorption spectrum within the range 6035-6210 cm(-1) was measured for the first time with a spectral resolution of 10 MHz. The reported line centre positions have an uncertainty of +/- 0.0005 cm(-1). The precise measurements of ethylene absorption cross-sections were carried out using the mixture of high purity ethylene and broadening gas (nitrogen) at the mixture ratio 1:50-1:200. Measurements were carried out at a mixture pressure of about 4.2 kPa.