Abstract： In this letter, a new derivation of Keldysh's formula is presented and a brief discussion about the comparison between the new derivation and the original one is given.
CHEN Baozhen. A NEW DERIVATION OF KELDYSHS FORMULA[J]. 中国物理快报, 1990, 7(5): 219-221.
CHEN Baozhen. A NEW DERIVATION OF KELDYSHS FORMULA. Chin. Phys. Lett., 1990, 7(5): 219-221.
1990, Vol. 7 
