01755nas a2200193 4500008004100000022001400041245010300055210006900158260000900227300001100236490000700247520108800254100002001342700001801362700001601380700001801396700001601414856013101430 2014 eng d a2469-992600aRelativistic equation-of-motion coupled-cluster method: application to closed-shell atomic systems0 aRelativistic equationofmotion coupledcluster method application  cAPR  a0425100 v893 a

We report our successful implementation of the relativistic equation-of-motion coupled-cluster (EOMCC) method. This method is employed to compute the principal ionization potentials (IPs) of closed-shell rare-gas atoms, He-like ions, Be-like ions, along with Na+, Al+, K+, Be, andMg. Four-component Dirac spinors are used in the calculations, and the one-and two-electron integrals are evaluated using the Dirac-Coulomb Hamiltonian. Our results are in excellent agreement with available measurements, which are taken from the National Institute of Science and Technology database. The accuracies of the calculations are estimated to be within one half of a percent for He-like and Be-like ions and 1% for the heavier systems. We also present results using the second-order many-body perturbation theory and random-phase approximation in the EOMCC framework. These results are compared with those of EOMCC at the level of single and double excitations in order to assess the role of the electron correlation effects in the intermediate schemes considered in our calculations.

1 aPathak, Himadri1 aSahoo, B., K.1 aDas, B., P.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-equation-motion-coupled-cluster-method-application-closed-shell-atomic-systems00680nas a2200181 4500008004100000245011800041210006900159260000800228300002300236490000700259100002000266700001700286700001800303700001600321700001800337700001600355856012700371 2014 eng d00aRelativistic equation-of-motion coupled-cluster method for the double-ionization potentials of closed-shell atoms0 aRelativistic equationofmotion coupledcluster method for the doub cJUL aArticle No. 0105010 v901 aPathak, Himadri1 aGhosh, Aryya1 aSahoo, B., K.1 aDas, B., P.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-equation-motion-coupled-cluster-method-double-ionization-potentials-closed02123nas a2200205 4500008004100000022001400041245011700055210006900172260008100241300001100322490000700333520133300340653002401673653001601697653002401713100001901737700001801756700001601774856012701790 2014 eng d a0953-407500aRelativistic spectroscopy of plasma-embedded Li-like systems with screening effects in two-body Debye potentials0 aRelativistic spectroscopy of plasmaembedded Lilike systems with  aTEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLANDbIOP PUBLISHING LTDcSEP a1757010 v473 a

The spectroscopic properties of Li atoms and Li-like Ca and Ti ions in the plasma environment are investigated using a relativistic coupled-cluster (RCC) method. Assuming that the plasma is of low density and very hot, we consider the Debye model with two approximations to account for the screening effects: (i) in the nuclear potential alone and (ii) in both the nuclear and the electron-electron interaction potentials. Also, calculations for the energies and the lifetimes of the atomic states are carried out for plasma-free systems to check their accuracy, after which they are investigated in the plasma environment. It is observed that screenings in the electron-electron interaction potentials stabilize the systems more than when the screenings are present only in the nuclear potential. Similarly, the blue and red shifts in the Delta n = 0 and Delta n not equal 0 transition lines (with the principal quantum number n) of the Li-like ions observed in the (i) approximation are altered in the (ii) approximation. The level crossings among the energy levels are observed for large screening effects and are found to be prominent in the states of higher orbital angular momentum. The lifetimes of many low-lying states of the allowed transitions are estimated by considering different plasma screening strengths.

10aatomic Spectroscopy10aDebye model10arelativistic method1 aDas, Madhulita1 aSahoo, B., K.1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-spectroscopy-plasma-embedded-li-systems-screening-effects-two-body-debye-001855nas a2200241 4500008004100000022001400041245016200055210006900217260008100286300001100367490000700378520090300385653002701288653003301315653003001348100002001378700001801398700002201416700001601438700001801454700001601472856012501488 2015 eng d a0953-407500aRelativistic equation-of-motion coupled-cluster investigation of the trends of single and double ionization potentials in the He and Be isoelectronic systems0 aRelativistic equationofmotion coupledcluster investigation of th aTEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLANDbIOP PUBLISHING LTDcJUN a1150090 v483 a

We employ a four-component spinor relativistic equation-of-motion coupled-cluster (EOMCC) method within the single-and double-excitation approximation to calculate the single ionization potentials (IPs) and double ionization potentials (DIPs) of the He and Be isoelectronic sequences up to Ne. The obtained results are compared with the available results from the National Institute of Standards and Technology (NIST) database to test the performance of the EOMCC method. We also present intermediate results at different levels of approximations in the EOMCC framework to gain insight of the effect of electron correlation. Furthermore, we investigate the dependence of the IPs and DIPs of these ions on the ionic charge and observe that these follow parabolic trends. Similarities between the trends of IPs and DIPs in both the classes of considered systems are categorically demonstrated.

10acoupled-cluster method10adouble ionization potentials10aequation-of-motion theory1 aPathak, Himadri1 aSahoo, B., K.1 aSengupta, Turbasu1 aDas, B., P.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-equation-motion-coupled-cluster-investigation-trends-single-and-double-1