Could Spontaneous Transitions be Spontaneous?
  It is considered to re-formulate quantum theory as it appears: A theory of continuous and causal time evolution, interrupted by discontinuous and stochastic jumps. To develop the (missing) theory of jumps a heuristic-phenomenological approach is suggested. Relying on a global reduction process, a hypothesis is introduced postulating spontaneous collapse of superpositions of states which describe spontaneous absorption or emission. The collapse probability determines a mean collapse time $\tau^c = b \hbar / \triangle E$, where $b$ is a dimensionless constant and $\triangle E$ is the difference in energy distribution between alternative branches. Ramsey atomic beam spectroscopy yields a lower bound on $b$ and avalanche photodiodes give an upper bound, such that $1.35\cdot 10^{11} < b < 3.8\cdot 10^{21}$. Ample opportunities for experimental improvements exist. 
Bernd A. Berg