Let ε < 0.

–Arthur H. Snell

There was an electron in gold
Who said, “Shall I do as I’m told?
Shall I snuggle down tight
With a brief flash of light
Or be Auger outside in the cold?”

Said the K-shell electron in gold,
“I’m thinking of leaving the fold
To be hit like a hammer
By an outgoing gamma.
In freedom I’ll live till I’m old.”

Said the K-shell electron in gold,
“I wonder if I might be bold
And make a slight shift
From this circular drift
And change this damned atom to platinum.”

If your physics needs a little help, the three stanzas refer to fluorescent yield, internal conversion, and electron capture, respectively.