Populations of excited states in flash-heated vapours

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Abstract
The populations of excited states in the vapours of barium and calcium produced by the flash pyrolysis technique have been investigated by means of the hook method. For low-lying states (within about 2 eV of the ground state) the populations some 500 mu s after the beginning of the pyrolysis flash were found to follow the Boltzmann distribution at a temperature which for our particular experimental conditions was about 5000 K. The reproducibility is such as to make this a suitable source for the determination of relative oscillator strengths for lines originating on these low-lying levels. The degree of ionization, however, is significantly below that to be expected in thermal equilibrium at this temperature.