What is the complete mechanism of reaction for sodium benzoate and ascorbic acid? What are the complete steps of reaction from sodium benzoate and ascorbic acid to benzene? I can't seem to visualize it, and, much less, find anything online regarding the actual steps of the reaction.

Additionally: how does it make use of, say Cu(II) or Fe(III) to complete the reaction? It seems that the reaction can only proceed with these present.
From Benzene production from decarboxylation of benzoic acid in the presence of ascorbic acid and a transition-metal catalyst:

$\ce {Cu^{2+} + H_2Asc \rightarrow Cu^+ + HAsc^.}$

$\ce {Cu^+ + O_2 \rightarrow Cu^{2+} + O_2^-}$

$\ce {2O_2^- + 2H^+ \rightarrow H_2O_2 + O_2}$

$\ce {Cu^+ + H_2O_2 \rightarrow Cu^{2+} + OH^- + OH^.}$

Then the hydroxyl radical reacts with benzonic acid as opposed to benzoate.