[a student]

in general interaction with neighbouring nuclear dipoles only causes a splitting of the signal if the nuclei maintain their spin orientation in B0 for a time longer than τ₀=1/J but in spin decoupling experiment we try to shortening this time by irradiating with a second frequency v₂ .
here I have 1 question:
 how does this 2nd radiator shorten this time?

[Yggdrasil]

I'm not completely sure of the answer, but could the second frequency be promoting stimulated emission?

[a student]

I'm not completely sure of the answer, but could the second frequency be promoting stimulated emission?

I,m not sure but it seems you are right.