Delay, Once Only

From,

$E_p=\hbar\left\{1-\sqrt{tan(\theta_v)}\right\}\cfrac{c}{x_c}$

for $0\lt\theta\lt45^o$,

$E_p\gt0$

emission is followed by absorption.

For $45^o\lt\theta\lt90^o$,

$E_p\lt0$

absorption is followed by emission, as a result there is a small delay before emission.

At $\theta=45^o$,

$E_p=0$

there is no emission, absorption occurs once of the initial excitation photon.

At $\theta=90^o$,

$E_p\to\infty$

Not probable, but $\small{\theta}$ can come close to ninety degrees.