From Table 1, one can see the oscillator strength (f), the transition velocity dipole moments, and the transition dipole moment along the long axis of the molecule (X) of the S0 → S1 electronic transition are both the largest for the two molecules, which indicate that the first excited state S1 is the strongest one-photon absorption. Also, the transitions S0 → S2 and S0 → S3 are relatively strong for the two molecules. A strong one-photon absorption state can be a strong 3PA state as well. If the transition energy between two states is larger than the three-photon energy of 1064 nm laser, 3PA can not take place. Consequently, the two transitions S0 → S1 (3.3318 ev) and S0 → S2 (3.4662 ev) of A may occur and the only transition S0 → S1 (3.3990 ev) of B may occur. The theoretical results just are consistent with the above experimental results.