Determination of the rate constant for vibrational-vibrational exchange in nitrogen under biharmonic excitation conditions

Experimental determination of the rate of V–V collisional relaxation in14N2in its ground (X1Σg+) electronic state between 77 and 300 K

“…This is mostly due to the great quality of the pioneering studies of Billing. The fact that the same figure was later obtained by a different author by means of an experiment 8 lends additional weight to this result, even although in the meantime other authors had conducted experiments 9,16 that yielded higher values of k. On the other hand, the original studies of Billing on N 2 -N 2 and other collisional systems were carried out in the seventies. In the following decades, as pointed out by other authors 7 and Billing himself, 2,21,22 great progress was made in the development of both better interaction potentials and better collisional models for N 2 -N 2 and other systems.…”

“…Despite the apparent simplicity of this energy exchange, there is a surprisingly large spread among the results obtained by different authors, whether through calculation or experiment, for the value of the rate constant k for this collisional process at 300 K. In the case of the calculations the reported values range from 2.90 Â 10 À4 Torr À1 ms À1 obtained by Billing 6 to 1.30 Â 10 À3 Torr À1 ms À1 calculated by Cacciatore. 7 The experimental results place k in an interval between a low value 8 of 2.90 Â 10 À4 Torr À1 ms À1 and a high value 9 of 3.2 Â 10 À3 Torr À1 ms À1 .…”

“…This is in turn due to the fact that 14 N 2 does not have a permanent dipole moment, which rules out the use of the most widespread techniques for both vibrational excitation from v = 0 to v = 1 and the subsequent spectroscopic monitoring of v = 1. In fact, all the prior experiments cited in this article have used the technique of stimulated Raman pumping (sometimes presented under other names like ''biharmonic excitation'' 9 ) for vibrational excitation to v = 1 followed by another Raman technique (typically CARS or spontaneous Raman spectroscopy) for monitoring of the v = 1 state. The instrumental complexity associated with this type of pump-probe Raman measurement helps explain the relatively small number of them found in the bibliography.…”

Mechanisms of Ionizational Nonequilibrium in Air Plasmas

“…The N2-N2 V-V exchange process has been studied experimentally at 300K by [36][37][38][39][40][41] and theoretically by semiclassical trajectory methods [42,43] and SSH theory [44,45]. These results are plotted in Figure 23.…”

“…On the other hand, measuring V-V probabilities for nitrogen is difficult because of the very weak absorption vibrational spectrum. Podobedov [36], Valyanskii et al [37,38], Suchkov and Shebeko [39] and Gordeev and Shakatov [41] monitored the relaxation of nitrogen vibrational levels using Raman methods. They obtained the rate constant fc°^_, by fitting their experimental results with solutions of the coupled kinetic equations describing the relaxation process.…”