01578nas a2200169   4500008004100000022001400041245011400055210006900169260007100238300001400309490000600323520089600329100001901225700001601244700001801260856013001278       2010                        eng d  a1549-961800aCalculation of dipole transition matrix elements and expectation values by vibrational coupled cluster method0 aCalculation of dipole transition matrix elements and expectation  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a3198-32040 v63 a<p>An effective operator approach based on the coupled cluster method is described and applied to calculate vibrational expectation values and absolute transition matrix elements. Coupled cluster linear response theory (CCLRT) is used to calculate excited states. The convergence pattern of these properties with the rank of the excitation operator is studied. The method is applied to a water molecule. Arponen-type double similarity transformation in extended coupled cluster (ECCM) framework is also used to generate an effective operator, and the convergence pattern of these properties is compared to the normal coupled cluster (NCCM) approach. It is found that the coupled cluster method provides an accurate description of these quantities for low lying vibrational excited states. The ECCM provides a significant improvement for the calculation of the transition matrix elements.</p>1 aBanik, Subrata1 aPal, Sourav1 aPrasad, Durga  uhttps://library.ncl.res.in/content/calculation-dipole-transition-matrix-elements-and-expectation-values-vibrational-coupled-0