Figure 3
Photoabsorption spectrum for the B1Σ+–X1Σ+(0,0) band of 12C16O, recorded with (a) the windowless cell at room temperature (blue), (b) the heated windowless cell (orange), and (c) the molecular jet setup (black). A reference room-temperature band oscillator strength was used to determine the column density and calibrate the absolute cross section (Stark et al., 1999a ); the instrumental spectral resolution is 0.23 cm−1. We assume that only v′′ = 0 is populated, except for the high-temperature spectrum for which 1.5% of the molecules are populating the first excited state. For the molecular jet, the backing and background pressures are 2 × 105 Pa and 0.6 Pa, respectively. The P and R branches of the rotational structure are clearly distinguishable; note how the J-level distribution depends on the temperature (see text for details). |