Highly predissociative levels of CH B 2Σ− state detected with two-color resonant four-wave mixing spectroscopy

Analysis of measured high-resolution doublet rovibronic spectra and related line lists of CH and OH

Detailed understanding of the energy-level structure of the quantum states as well as of the rovibronic spectra of the ethylidyne (CH) and the hydroxyl (OH) radicals is mandatory for a...

Empirical Line Lists in the ExoMol Database

The ExoMol database aims to provide comprehensive molecular line lists for exoplanetary and other hot atmospheres. The data are expanded by inclusion of empirically derived line lists taken from the literature for a series of diatomic molecules, namely CH, NH, OH, AlCl, AlF, OH + , CaF, MgF, KF, NaF, LiCl, LiF, MgH, TiH, CrH, FeH, C 2 , CP, CN, CaH, and triplet N 2 . Generally, these line lists are constructed from measured spectra using a combination of effective rotational Hamiltonian models for the line positions and ab initio (transition) dipole moments to provide intensities. This work results in the inclusion of 22 new molecules (36 new isotopologues) in the ExoMol database.

Two-color resonant four-wave mixing spectroscopy of highly predissociated levels in the ÃA12 state of CH3S

We report results of two-color resonant four-wave mixing experiments on highly predissociated levels of the methylthio (or thiomethoxy) radical CH3S in its first excited electronic state A 2A1. Following photolysis of jet-cooled dimethyl disulfide at 248 nm, the spectra were measured with a hole-burning scheme in which the probe laser excited specific rotational transitions in band 3(3). The spectral simplification afforded by the two-color method allows accurate determination of line positions and homogeneous linewidths, which are reported for the C-S stretching states 3v(v=3-7) and combination states 1(1)3v(v=0-2), 2(1)3v(v=3-6), and 1(1)2(1)3v(v=0,1) involving the symmetric CH3 stretching (nu1) mode and the CH3 umbrella (nu2) mode. The spectra show pronounced mode specificity, as the homogeneous linewidth of levels with similar energies varies up to two orders of magnitude; nu3 is clearly a promoting mode for dissociation. Derived vibrational wave numbers omega1', omega2', and omega3' of the A state agree satisfactorily with ab initio predictions.

Investigation of soot by two-colour four-wave mixing

A novel technique has been used for the temporally resolved investigation of the interaction of laser radiation and soot in a flame. Based on established soot vaporisation models we developed a framework to calculate the two-colour four-wave mixing signal obtained in an acetylene/air diffusion flame at atmospheric pressure. The signal comprises a contribution due to soot and, depending on the wavelength of the probe laser, a contribution because of C2, which is generated by vaporising soot. For both parts of the signal we found a good agreement between measured and calculated power dependency. Furthermore, we measured spatial profiles of the signal in a Wolfhard-Parker slot burner. By analysing the different signal contributions we found that depending on the location within the flame there are particles with different C2 yield.