High-resolution absorption cross sections of C2H6 at elevated temperatures

Abstract

Infrared absorption cross sections near 3.3 µm have been obtained for ethane, C 2 H 6 . These were acquired at elevated temperatures (up to 773 K) using a Fourier transform infrared spectrometer and tube furnace with a resolution of 0.005 cm −1 . The integrated absorption was calibrated using composite infrared spectra taken from the Pacific Northwest National Laboratory (PNNL). These new measurements are the first high-resolution infrared C 2 H 6 cross sections at elevated temperatures.

New investigation of the ν3 C–H stretching region of 12CH4 through the analysis of high temperature infrared emission spectra

“…The emergence of new experimental techniques such as the High Enthalpy Source (HES), developed by R. Georges and coworkers, coupled to a high-resolution Fourier transform spectrometer (FTS) allows the recording of high temperature emission spectra of polyatomic molecules (C 2 H 2 and CH 4 ) [33,34,35] up to about 2000 K. Recently, a new experimental setup coupling the HES to a cw-cavity ring-down spectrometer has been developed by the same group to investigate rotationally cold hot bands of polyatomic molecules in the 1.5-1.7 µm region [36]. Hargreaves et al developed an original approach to produce emission-corrected FTIR transmittance spectra of hot gases such as methane [37] and ethane [38]. Such high temperature spectra are of great relevance because they bring considerable information on high J-transitions -up to J = 30 -and hot bands originating from highly excited polyads.…”

Mid-Infrared Polarization Spectroscopy Measurements of Species Concentrations and Temperature in a Low-Pressure Flame

“…The HITRAN database line list for C 2 H 6 is not complete in this spectral region, containing only data for the high intensity Q-branches of the ν 7 band. 25 The absorption spectra of C 2 H 6 in this spectral range has been investigated at room temperature 56 and elevated temperatures, 49,51,52 showing the existence of several P- and R-branch transitions between the Q-branches. These transitions can probably account for many of the unidentified lines in the IRPS spectrum in Fig.…”

High enthalpy source dedicated to quantitative infrared emission spectroscopy of gas flows at elevated temperatures

“…Low-resolution experiments [11][12][13][14] (typically >1 cm −1 ) give access to the thermal radiance of whole vibrational bands, while highresolution is required to extract line-by-line parameters. The positions, 1,3,[15][16][17][18][19] integrated absorption cross sections [20][21][22][23][24] (also called absolute line intensities), and shapes of lines can therefore be measured at high temperature. What makes high-temperature measurements especially crucial is their ability to give access to spectroscopic parameters associated with lines of high-J rotational quantum numbers, as well as with rotation-vibration lines belonging to hot bands involving highly excited vibrational states, which are generally lacking in room temperature spectroscopic databases such as high-resolution transmission molecular absorption (HITRAN) 25 and therefore cannot be extrapolated at high temperature.…”

“…12,42 Furthermore, absorption experiments conducted at elevated temperatures have to take into account the thermal emission of the gas itself, which is superimposed to the absorption signal induced by the external source of photons. Successive recording of the absorption signal (external source activated) and the emission signal of the gas (external source deactivated) allows overcoming this problem 21,22,29 and notably increases the accuracy of the recorded cross sections, reaching a few percent. 21 Another effect impacting emission measurements arises from nonoptically thin gas samples, which are prone to self-absorption effects.…”

“…Successive recording of the absorption signal (external source activated) and the emission signal of the gas (external source deactivated) allows overcoming this problem 21,22,29 and notably increases the accuracy of the recorded cross sections, reaching a few percent. 21 Another effect impacting emission measurements arises from nonoptically thin gas samples, which are prone to self-absorption effects. The intensity of the strong emission lines is more affected than the weak ones 43 (see Sec.…”