Quantum control study of multilevel effect on ultrafast isotope-selective vibrational excitations

Kurosaki, Yuzuru; Yokoyama, Keiichi  ; Yokoyama, Atsushi

Quantum optimal control calculations have been carried out for isotope-selective vibrational excitations of the cesium iodide (CsI) molecule. Considering a gaseous isotopic mixture of CsI and CsI, the initial state is set to the condition that both CsI and CsI are in the vibrational ground level ( = 0) and the target state is that CsI is in the = 0 level while CsI in the first-excited level ( = 1). We find, using the density-matrix formalism, that perfect isotope-selective excitations for multilevel systems including more than ten lowest vibrational states can be completed in much shorter time scales than those for two-level systems. This multilevel effect comes from the large isotope shifts of the vibrational levels of 1. To check the reliability of the calculation we also employ the conventional wave-packet formalism and obtain almost the same results as those with the density-matrix formalism.