optics - How does infrared light 'erase' phosphorescence on zinc sulfide?

I found some sheets of zinc sulfide in my basement that phosphoresce green for up to 24 hours or so after exposure to bright light in the violet range or shorter. One of the first things I tried was drawing on it with a violet laser pointer (405nm, 5mW) and as expected it draws bright lines. What I found more surprising was that I can 'erase' the phosphorescent lines if I focus my green laser onto them. I've determined with some color filters that it's infrared at 1064nm leaking from the green laser causing the erasure. This erasure does not appear to damage the panel in any way, once erased the erased spot can be lit back up to full brightness normally.

How is this infrared light erasing the panel, and how effective would other infrared wavelengths be at doing this?

Answer

Thanks to @Manishearth for the edit

In normal phosphorescence, the atoms are in a "metastable" state--where electrons are in a higher energy level, but do not immediately come to ground state due to partial stability. The electrons come down slowly, giving rise to the (relatively) long lasting glow.

The IR light frees away the electrons from the shallow metastable trap. It's like the usual chemical reaction, where the IR light provides enough activation energy to overcome the barrier. Basically, the IR light promotes the electrons to a higher, non-metastable "energy level" (virtual state). From here, the electron jumps down nearly immediately--dumping all its energy. So, instead of the electrons trickling down like in normal phosphescence, they all come down in a torrent.

The same experiment was performed by this guy: http://ajp.aapt.org/resource/1/ajpias/v29/i3/pxxv_s2

The effect has been explained by the assumption that the long-wave radiation frees electrons from shallow trapping centers into which they have fallen after being excited to the conduction band by the ultraviolet light. The freed electrons recombine quickly with ionized luminous centers with the emmision of light. More recent investigations indicate that probably other processes also are involved.