Lecture · Stanford
Penetration factor for slowly varying barriers – David Miller
David Miller Quantum Mechanics Courses · David A. B. Miller
Miller slices a smoothly varying barrier into thin layers whose internal boundary matrices become the identity, leaving an amplitude factor exp(−∫κ(z)dz), with κ = √(2m(V(z) − E))/ħ, and a tunnelling probability, his "penetration factor", of an edge-dependent prefactor times exp(−2∫κ(z)dz). That is section 2's WKB rule (twice the area under κ in the exponent) and the engine of Gamow's calculation in section 3; it builds on his transfer-matrix lecture (33c), so treat it as a stretch goal.