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The terms in the master equation for vibrational relaxation of anharmonic oscillators are ordered according to the rates of the relaxation processes (vibrational exchange, vibrational-energy transfer to translation). The population distributions in the master equation are expanded about their values when the vibration-vibration mechanism is the only one present. An analytic expression is given for the distribution maintained by the vibration-vibration mechanism. In the limiting case of the simple harmonic oscillator, this distribution reduces to the usual Boltzmann-like distribution defined by a single vibrational temperature. The general solution also applies to a mixture of simple-harmonic-oscillator gases of different fundamental frequencies. For such a mixture, each gas relaxes in a Boltzmann-like distribution, but the different gases have different (but related) vibrational temperatures at any given time. The relaxation of the first moment of the distribution function also has been investigated. Anharmonicity causes a marked departure from the Landau-Teller model of vibrational relaxation under conditions of high vibrational energy, coupled with low translational temperature. For such conditions, the populations of the lower vibrational states can be considerably lower than those predicted by the Landau-Teller model. Furthermore, the over-all energy relaxation rate can be accelerated.

Wildfires that spread into wildland–urban interface (WUI) communities present significant challenges on several fronts. In the United States, the WUI accounts for a significant portion of wildland fire suppression and wildland fuel treatment costs. Methods to reduce structure losses are focussed on fuel treatments in either wildland fuels or residential fuels. There is a need for a well-characterised, systematic testing of these approaches across a range of community and structure types and fire conditions. Laboratory experiments, field measurements and fire behaviour models can be used to better determine the exposure conditions faced by communities and structures. The outcome of such an effort would be proven fuel treatment techniques for wildland and residential fuels, risk assessment strategies, economic cost analysis models, and test methods with representative exposure conditions for fire-resistant building designs and materials.

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