Abstract
A selection rule is derived for m1=0→m2=0 transitions in atom‐symmetric top collisions when the final and initial quantization axes are parallel to the initial relative velocity vector. The scattering amplitude and differential and integral cross sections for the j1k1ε10 →j2k2ε20 transition vanish unless ε1(−1)j1+k12(−1)j2+k2 where ε is the parity of the inversion level.