When 2 particles of size n=1 coalesce 2 photons E1→2 are emitted, and when 2 particles of sizes n=1 and n=2 coalesce 2 different photons E1→3 and E2→3 are emitted.
This is not the simple scheme where emissions as the result of hops from energy level to energy level has equal intensity, but in the example above, E1→2 has twice the intensity of E1→3 and E2→3.
The plot below shows ((x+1)^(1/3)-x^(1/3))/(((x+1)*x)^1/3), ((x+2)^(1/3)-x^(1/3))/(((x+2)*x)^1/3) and ((x+3)^(1/3)-x^(1/3))/(((x+3)*x)^1/3).
where particle of size n=1, n=2 and n=3 coalesce with particle of size n=x.
We see that the highest energy transition occurs with E1→n=large, when a basic particle aψc (ie. n=1) coalesces with a large particle n→77. Two photons are released E1→n=large and Elarge→large+1.
Emission occurs in bands as n=x increases and such bands narrows with increasing n=x.
In the graph above, the top most three horizontal lines maroon, red and blue correspond to x=1. The next band of maroon, red and blue correspond to x=2. Each band progressively narrows as x increases.
As x increases, all graph approaches asymptotically to zero, ie as x increases all emissions due to the coalescence of particles of various sizes, n approaches zero.
Good night.