Energy pooling in an equilibrium-coupled system between Ca[4s3d(1D2)] and Mg[3s3p(3Pj)] atoms following pulsed dye-laser excitation
Abstract
We present a kinetic study of energy pooling in the equilibrium-coupled system: Ca[4s3d(1D2)]+ Mg[3s2(1S0)]⇌ Ca[4s2(1S0)]+ Mg[3s3p(3PJ)] following pulsed dye-laser excitation of both Mg(3PJ) and Ca(1D2) atoms at λ= 457.1 nm. [Mg(3P1)â†� Mg(1S0)] and λ= 457.5 nm [Ca(1D2)â†� Ca(1S0)] in the presence of helium across the temperature range 800–1100 K. Quantitative characterisation of decay profiles for Mg(3PJ) and Ca(1D2) by time-resolved emission measurements at the above wavelengths using boxcar integration indicates the effectively instantaneous establishment and maintenance of the near-resonant equilibrium under all conditions of temperature and pressure via the observed equality in the first-order decay coefficients for removal of both states. Energy pooling into some 16 higher-lying states of magnesium and calcium, including atomic levels close to the energetically accessible limit, were observed and their temporal behaviour characterised. With the exceptions of Mg[3s4s(3S1)] and Ca[4s4p(1P1)] atoms, all these pooled states exhibited first-order kinetic behaviour. Measured first-order decay coefficients for these pooled states were found to be always twice those of the energy store states, indicating their production via collisions involving the metastable states Mg(3PJ), Ca(1D2) and possibly Ca(3PJ). Initial relative populations of energy-pooled states were estimated in all cases and found to lie in the range 10–4–10–6, thus constituting a small ‘bleed-off’ from the and Ca(1D2) energy stores without disturbing the observed first-order decay of these two states in the equilibrium-coupled system.