Vibrational distribution inverse population

Electronically excited NH 2 ) has been detected [448] as a product of the reaction H + HN3. The NH is formed with bending vibrations up to v2 = 15 excited, implying that more than 80% of the available energy can go into vibrational excitation of the NHf. There is no evidence of population inversion in the vibrational distribution. The emission from NH ( , 3II), also observed in the experiment, is attributed to the reaction H + N3. 

From fig. 8, it is seen that the shapes of the vibrational distributions are smooth and decidedly non-thermal in character. In the case of BaCl, BaBr and Bal, there is definate vibrational population inversion. The rotational distributions are less well characterized but the BaF distribution appears to be described quite satisfactorily by a temperature. 

This vibrational distribution for abstrartion reactions is similar to that obtained on the first excited state surface, l A" (not shown here). There is a strong population inversion and only v = 3,4 have appreeiable cross sections. 

Table 2. Energy distribution and population inversion in reactions of the type A-fBC, E /Etot = fraction of the total heat of reaction going into product vibration... 

Figure 8 shows for the reaction 0( D) + H2(t = 0,j = 0) OE v, j ) + H reaction the vibrational distribution (ICS as a function of the i)roduct vibrational quantum number v for five collision energies (25, 56, 84, 100 and 137 meV). At all energies, the most populated vibrational level is v = 0. ICS decreases when the j)roduct vibrational (luantum number v increases. This decrease reflects the diminution of open rotational states in a given vibrational manifold. For all energies, the distributions arc vibrationally cold and these non-inverted vibrational I)Oi)ulations arc in sharp contrast with those computed for abstraction reactions such as F -h H2 —> FH + H [29] and F - - D2 —t FD + D [9] abstraction reactions which show a vibrational population inversion. 

Vibrational distribution function (3-141) can include a domain of inverse population... 

The OH vibrational distributions from the HQ [89] and HBr [94] reactions are also strongly inverted. The extent of the inversion in these results is surprising in view of the generally-accepted interpretation that these reactions, like the H2 case, also involve insertion of the 0( D) atom into the molecular bond. The extent of this inversion is clear, however, from the time-dependent spectra of the products from the 0( D) + HQ reaction shown in Fig. 3. These were recorded using the TRFTS instrument described in the Experimental Section, imder conditions for which the gas kinetic collision time is about 10 is. The earliest OH spectrum at 20 [is shows that the initial vibrational distribution peaks strongly in OH(v =3), and has virtually no population in v =l. (The frequencies of the P-branch lines of each vibrational level are indicated). This excitation is coUisionally relaxed in subsequent spectra. 

The production of MO in ground and electronically excited states by the reactions of M + 02, NO, N20, N02, 03 and S02 has been studied by laser-induced fluorescence and visible chemiluminescence methods. The reactions M + 02 have been particularly well studied. For Y + 02 and Sc + 02, emission is observed [389] from the A2Tl and A 2A states of MO and the branching ratios for population of these states are statistical. The MO vibrational population distribution in the A2Yli/2 state is statistical, whilst the distributions for the other states show inversion. The MO (A) rotational distributions can be fitted by Boltzmann forms with temperatures which differ from the vibrational temperatures [392]. For... 

This type of distribution, which presents an inversion at a vibrational quantum number given by dj = Tg/25 81 + 0.5 predicts a high population of excited vibrational levels for i/Tg > 1. [In Eq. (4) E10 is the energy of level 1 and 5 is the anharmoni-city of the molecule]. 

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