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-closed01580nas a2200193 4500008004100000022001400041245011200055210006900167260007900236300002300315490000700338520082300345100002001168700001801188700002201206700001801228700001601246856012401262 2014 eng d a1050-294700aRelativistic equation-of-motion coupled-cluster method for the ionization problem: application to molecules0 aRelativistic equationofmotion coupledcluster method for the ioni aONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USAbAMER PHYSICAL SOCcDEC aArticle No. 0625010 v903 a

We report the implementation of the four-component spinor relativistic equation-of-motion (EOM) coupled-cluster method within the single- and double-excitation approximation to calculate the ionization potential of molecules. We have applied this method to calculate vertical ionization potentials of the molecules XH (X = F, Cl, Br, I) along with Cl-2 and Br-2 in their closed-shell configuration. We have also presented intermediate results using the second-order many-body perturbation-theory level in the EOM framework to understand the role of electron correlation. All the calculated values are compared with the available experimental results. Our results are found to be in good agreement with sophisticated experiments, and relative deviation of less than 1% is achieved for all the considered systems.

1 aPathak, Himadri1 aSasmal, Sudip1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-equation-motion-coupled-cluster-method-ionization-problem-application-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-100625nas a2200169 4500008004100000245009100041210006900132260000800201300002300209490000700232100001800239700002000257700002200277700001800299700001600317856012200333 2015 eng d00aRelativistic extended coupled cluster method for magnetic hyperfine structure constant0 aRelativistic extended coupled cluster method for magnetic hyperf cFEB aArticle No. 0225120 v911 aSasmal, Sudip1 aPathak, Himadri1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-extended-coupled-cluster-method-magnetic-hyperfine-structure-constant01797nas a2200193 4500008004100000022001400041245011700055210006900172260007900241300001100320490000700331520104800338100001801386700002001404700002201424700001801446700001601464856012301480 2016 eng d a2469-992600aRelativistic coupled-cluster study of RaF as a candidate for the parity- and time-reversal-violating interaction0 aRelativistic coupledcluster study of RaF as a candidate for the  aONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USAbAMER PHYSICAL SOCcJUN a0625060 v933 a

We have employed both the Z-vector method and the expectation-value approach in the relativistic coupled-cluster framework to calculate the scalar-pseudoscalar (S-PS) P, T-odd interaction constant W-s and the effective electric field E-eff experienced by the unpaired electron in the ground electronic state of RaF. Further, the magnetic hyperfine structure constants of Ra-223 in RaF and Ra-223(+) are also calculated and compared with the experimental values wherever available to judge the extent of the accuracy obtained with the employed methods. The outcome of our study reveals that the Z-vector method is superior to the expectation-value approach in terms of accuracy obtained for the calculation of ground-state property. The Z-vector calculation shows that RaF has a high Eeff (52.5 GV/cm) and W-s (141.2 kHz), which makes it a potential candidate for the electric dipole moment of the electron (eEDM) experiment. An estimation of uncertainty associated with our final results is made, and it is found that it lies below 10%.

1 aSasmal, Sudip1 aPathak, Himadri1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-coupled-cluster-study-raf-candidate-parity-and-time-reversal-violating01514nas a2200181 4500008004100000245009500041210006900136260000800205300001100213490000900224520088600233100002001119700001801139700002201157700001801179700001601197856011901213 2016 eng d00aRelativistic equation-of-motion coupled-cluster method for the electron attachment problem0 aRelativistic equationofmotion coupledcluster method for the elec cJAN a94-1000 v10763 a

The article considers the successful implementation of relativistic equation-of-motion coupled cluster method for the electron attachment problem (EA-EOMCC) at the level of single- and double- excitation approximation. The implemented relativistic EA-EOMCC method is employed to calculate ionization potential values of alkali metal atoms (Li, Na, K, Rb, Cs, Fr) and the vertical electron affinity values of LiX (X = H, F, Cl, Br), NaY (Y = H, F, Cl) starting from their closed-shell configuration. Both four component and exact two-component calculations are done for all the opted systems. Further, we have shown the effect of spin-orbit interaction considering the atomic systems. The results of our atomic calculations are compared with the values from the NIST database and the results are found to be very accurate (<1%). (C) 2015 Elsevier B.V. All rights reserved.

1 aPathak, Himadri1 aSasmal, Sudip1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-equation-motion-coupled-cluster-method-electron-attachment-problem01816nas a2200157 4500008004100000245011000041210006900151260000800220490000800228520121300236100002201449700002201471700001801493700001601511856013101527 2019 eng d00aRelativistic coupled-cluster investigation of parity (P) and time-reversal (T) symmetry violations in HgF0 aRelativistic coupledcluster investigation of parity P and timere cFEB0 v1503 a

We employ the Z-vector method in the four-component relativistic coupled-cluster framework to calculate the parity (P) and time-reversal (T) symmetry violating scalar-pseudoscalar nucleus-electron interaction constant (W-s), the effective electric field (E-eff) experienced by the unpaired electron, and the nuclear magnetic quadrupole moment-electron interaction constant (W-M) in the open-shell ground electronic state of HgF. The molecular frame dipole moment and the magnetic hyperfine structure (HFS) constant of the molecule are also calculated at the same level of theory. The outcome of our study is that HgF has a high value of E-eff (115.9 GV/cm), W-s (266.4 kHz), and W-M (3.59 x 10(33) Hz/e cm(2)), which shows that it can be a possible candidate for the search of new physics beyond the standard model. Our results are in good agreement with the available literature values. Furthermore, we investigate the effect of the basis set and the virtual energy functions on the computed properties. The role of the high-energy virtual spinors is found to be significant in the calculation of the HFS constant and the P,T-odd interaction coefficients. Published under license by AIP Publishing.

1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-coupled-cluster-investigation-parity-p-and-time-reversal-t-symmetry-violations01799nas a2200217 4500008004100000022001400041245007200055210006900127260000800196300001100204490000700215520109000222653004301312653002501355653002501380100002201405700002201427700001801449700001601467856009801483 2020 eng d a0953-407500aRelativistic coupled-cluster study of BaF in search of CP violation0 aRelativistic coupledcluster study of BaF in search of CP violati cJUL a1351020 v533 a

BaF is one of the potential candidates for the experimental search of the electric dipole moment of the electron (eEDM). The NL-eEDM collaboration is building a new experimental set up to measure the eEDM using the BaF molecule (The NL-eEDM collaboration, 2018 Eur. Phys. J. D 72: 197). To analyze the results of such an experiment, one would require the accurate value of the molecular P, T-odd interaction parameters that cannot be measured from any experiment. In this work, we report the precise value of the P, T-odd interaction parameters of the BaF molecule obtained from the four-component relativistic coupled-cluster calculations. We also calculate the hyperfine structure (HFS) constants of the same molecule to assess the reliability of the reported molecular parameters. The calculated HFS constants show good agreement with the available experimental values. Further, the systematic effects of electron-correlation along with the roles of inner-core electrons and the virtual energy functions in the calculation of the studied properties of BaF are investigated.

10aelectric dipole moment of the electron10aelectron-correlation10aRelativistic effects1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-coupled-cluster-study-baf-search-cp-violation01561nas a2200181 4500008004100000022001400041245011000055210006900165260000900234300001100243490000800254520091100262100002201173700002201195700001801217700001601235856012801251 2020 eng d a2469-992600aRole of electron correlation in the P, T-odd effects of CdH: a relativistic coupled-cluster investigation0 aRole of electron correlation in the P Todd effects of CdH a rela cMAR  a0325050 v1013 a

We investigate the parity (P) and time-reversal (T) symmetry violating effects in the CdH molecule and perform the relativistic coupled-cluster calculation of the molecular parameters-E-eff, W-s, and W-M-related to the electric dipole moment of electron (eEDM) interaction, the scalar-pseudoscalar (S-PS) nucleus-electron neutral current coupling, and the nuclear magnetic quadrupole moment (MQM) interaction with electrons, respectively. We also compute the molecular dipole moment and the magnetic hyperfine structure coupling constant of CdH. The values of E-eff, W-s, and W-M obtained by us in the said molecule are 12.2 GV/cm, 14.0 kHz, and 0.82 x 10(33) Hz/e cm(2), respectively, within an uncertainty of 10%. Furthermore, we study the trend of electron-correlation in the computed properties of CdH and that of the P, T-odd parameters in the group-12 monohydrides (i.e., ZnH, CdH, and HgH).

1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/role-electron-correlation-p-t-odd-effects-cdh-relativistic-coupled-cluster-investigation01585nas a2200253 4500008004100000022001400041245014100055210006900196260000800265300001100273490000800284520070400292653003200996653002201028653001601050653002701066653002001093653001501113100001601128700002401144700001601168700001801184856012901202 2021 eng d a0020-760800aResonance study: effect of partial triples excitation using complex absorbing potential-based Fock-space multi-reference coupled cluster0 aResonance study effect of partial triples excitation using compl cSEP ae267380 v1213 a

Resonances are metastable states with finite lifetime. They play important role in physics, chemistry and biology. The theoretical calculation of resonance state is a challenging problem. In this paper we have studied the shape resonance of Be, Mg, N-2 and CO. We have used correlated independent particle approximation to the Fock space multi-reference coupled cluster singles-doubles with third-order triples (CAP-CIP-FSMRCCSD(T)) method augmented by complex absorption potential. The resonance energy and decay widths are obtained by solving a non-Hermitian eigen-value problem within FSMRCC framework. The effects of the lowest order triples on the resonance energy and decay are studied.

10acomplex absorbing potential10aelectron affinity10aFock&\#820810anegative ion resonance10apartial triples10aspace MRCC1 aJana, Irina1 aBasumallick, Suhita1 aPal, Sourav1 aVaval, Nayana uhttps://library.ncl.res.in/content/resonance-study-effect-partial-triples-excitation-using-complex-absorbing-potential-based01793nas a2200253 4500008004100000022001400041245010000055210006900155260000800224300000700232490000800239520093800247653002701185653001701212653002401229653002701253653002501280100002201305700002801327700002501355700001801380700001601398856012501414 2023 eng d a1432-881X00aRelativistic coupled-cluster study of SrF for low-energy precision tests of fundamental physics0 aRelativistic coupledcluster study of SrF for lowenergy precision cFEB a150 v1423 a

SrF, being a laser-coolable molecule, can be an interesting system for spectroscopic tests of fundamental physics. We present an electronic structure study of this molecule within the four-component relativistic coupled-cluster singles and doubles (RCCSD) framework and employ the RCCSD-based methods to compute its molecular-frame dipole moment and core properties such as hyperfine structure coupling constant and molecular P, T-odd electronic structure parameters that are of great importance for the high-precision tests of fundamental physics. The impact of basis set size, Hamiltonian and nuclear model on the property calculation of SrF is also investigated. The computed results are in good agreement with the available experimental values. The present study shows that the SrF molecule could be useful for high-precision molecular experiments to explore physics beyond the Standard Model of elementary particles.

10aCoupled cluster theory10aCP violation10aHyperfine structure10aMolecular spectroscopy10aRelativistic effects1 aTalukdar, Kaushik1 aBuragohain, Haimyapriya1 aNayak, Malaya, K. K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-coupled-cluster-study-srf-low-energy-precision-tests-fundamental-physics01953nas a2200169 4500008004100000022001400041245013000055210006900185260000900254300001100263490000800274520132000282100001601602700001701618700001801635856013001653 2024 eng d a0021-960600aRelaxation of the 2a1 ionized water dimer: an interplay of intermolecular Coulombic decay (ICD) and proton transfer processes0 aRelaxation of the 2a1 ionized water dimer an interplay of interm cJUN  a2143020 v1603 a

This article investigates the relaxation dynamics of the ionized 2a(1) state of a water molecule within a water dimer. The study was motivated by findings from two previous pieces of research that focused on the relaxation behaviors of the inner-valence ionized water dimer. The present study discloses an observation indicating that water dimers display specific fragmentation patterns following inner-valence ionization, depending on the position of the vacancy. Vacancies were created in the 2a(1) state of the proton-donating water molecule (PDWM) and proton-accepting water molecule (PAWM). Utilizing Born-Oppenheimer molecular dynamics simulations, the propagation of the 2a(1) ionized state was carried out for both scenarios. The results revealed proton transfer occurred when the vacancy resided in the PDWM, accompanied by the closing of decay channels for O-H bond distance (RO-H) > 1.187 & Aring; (matching Richter et al.'s findings). Conversely, when vacancy was on PAWM, we observed no closing of decay channels (aligning with Jahnke et al.'s findings). This difference translates to distinct fragmentation pathways. In PDWM cases, 2a(1) state ionization leads to H3O+ -OH center dot formation. In contrast, PAWM vacancies result in decay pathways leading to H2O+-H(2)O(+ )products.

1 aKumar, Ravi1 aGhosh, Aryya1 aVaval, Nayana uhttps://library.ncl.res.in/content/relaxation-2a1-ionized-water-dimer-interplay-intermolecular-coulombic-decay-icd-and-proton01944nas a2200181 4500008004100000022001400041245011500055210006900170260000800239300001400247490000700261520128600268100002201554700002201576700001801598700001601616856013001632 2025 eng d a1549-961800aRelativistic extended-coupled-cluster calculations of P , T -odd sensitivity parameters for diatomic molecules0 aRelativistic extendedcoupledcluster calculations of P T odd sens cMAY a5481-54890 v213 a

We demonstrate the first application of the four-component relativistic extended-coupled-cluster (ECC) method, a variational approach, to determine the P , T -odd molecular electronic structure parameters necessary for high-precision spectroscopic measurements on ultracold molecules. We calculate the P , T -odd sensitivity parameters for two moderately heavy, laser-coolable diatomic molecules (SrH and SrF), as well as two relatively lighter open-shell molecules (CaH and CaF) in their ground electronic state, 2 Sigma 1/2. The hyperfine structure constants of 87Sr in the SrF and SrH molecules are also computed and compared with available experimental results to assess the accuracy of our calculations. Furthermore, we examine the roles of electron correlation, relativity, basis set, and virtual spinors in ECC calculations of the sensitivity parameters. Our study reveals that the ECC method is a reliable technique for studying P , T -odd properties of diatomic molecules such as CaH, CaF, SrH and SrF, yielding results in very good agreement with those obtained using two widely employed analytic approaches: the Z-vector technique and the linear expectation-value method within the relativistic single-reference coupled-cluster singles and doubles framework.

1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-extended-coupled-cluster-calculations-p-t-odd-sensitivity-parameters-diatomic