01296nas a2200181 4500008004100000245013600041210006900177260000800246300001400254490000800268520061000276100001800886700002200904700002200926700001800948700001600966856013200982 2016 eng d00aCalculation of hyperfine structure constants of small molecules using Z-vector method in the relativistic coupled-cluster framework0 aCalculation of hyperfine structure constants of small molecules  cOCT a1671-16750 v1283 aThe Z-vector method in the relativistic coupled-cluster framework is employed to calculate the parallel and perpendicular components of the magnetic hyperfine structure constant of a few small alkaline earth hydrides (BeH, MgH, and CaH) and fluorides (MgF and CaF). We have compared our Z-vector results with the values calculated by the extended coupled-cluster (ECC) method reported in Phys. Rev. A 91 022512 (2015). All these results are compared with the available experimental values. The Z-vector results are found to be in better agreement with the experimental values than those of the ECC values.1 aSasmal, Sudip1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/calculation-hyperfine-structure-constants-small-molecules-using-z-vector-method-relativistic01900nas a2200181 4500008004100000022001400041245011100055210006900166260000800235490000700243520124500250100002201495700001801517700002201535700001801557700001601575856012701591 2018 eng d a2469-992600aCorrelation trends in the magnetic hyperfine structure of atoms: a relativistic coupled-cluster case study0 aCorrelation trends in the magnetic hyperfine structure of atoms  cAUG0 v983 a

The role of electron correlation in the hyperfine structure of alkali metals and alkaline earth metal monopositive ions in their ground electronic configuration is investigated using the Z-vector method in a relativistic coupled-cluster regime within the singles and doubles approximation. The systematic effects of core-correlating functions, polarization of core electrons, and high-lying virtual functions on core electrons correlation are studied. The study reveals that the core-correlating function plays a significant role in core polarization and thus is very important for precise calculation of the wave function near the nuclear region. The inner-core electrons (1s-2p) require very high virtual energy functions for proper correlation. Therefore, the all-electron correlation treatment and the inclusion of higher-energy virtual functions are the key factors for precise calculation of the hyperfine structure constant of atoms. Our calculated values are in excellent agreement with the available experimental values, which also implies that the wave function produced by the Z-vector method is accurate enough for further calculation of the parity- and time-reversal symmetry-violating properties in atoms and molecules.

1 aTalukdar, Kaushik1 aSasmal, Sudip1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/correlation-trends-magnetic-hyperfine-structure-atoms-relativistic-coupled-cluster-case01790nas a2200181 4500008004100000022001400041245008600055210006900141260000900210300001100219490000700230520118200237100002201419700002201441700001801463700001601481856011101497 2019 eng d a2469-992600aNuclear parity- and time-reversal-symmetry violation in the (HgH)-Hg-201 molecule0 aNuclear parity and timereversalsymmetry violation in the HgHHg20 cMAR  a0325030 v993 a

Investigation of the nuclear magnetic quadrupole moment (MQM) is an excellent way to reveal the new physics in the hadron sector of matter. Therefore, we investigate the violation of parity (P) and time-reversal (T) invariance induced by the MQM of the( 201) Hg nucleus in the HgH molecule, which has been proposed as a very promising candidate for the experimental search of the electric dipole moment of electron [M. G. Kozlov and A. Derevianko, Phys. Rev. Lett. 97, 063001 (2006)]. We report the precise value of the molecular parameter, W-M, associated with the P, T-odd nuclear MQM-electron interaction in (HgH)-Hg-201 using the four-component relativistic coupled-cluster method. This parameter is required to interpret the experimental P, T-odd frequency shift in terms of the MQM of nuclei. Furthermore, the magnetic hyperfine structure (HFS) constants of the molecule are computed at the same level of theory. We also study the role of core-correlating functions and the virtual energy functions in the calculations of the HFS constant and W-M. The most reliable value of W(M )in HgH is obtained as 3.22 x 10 (33) Hz/e cm (2) with an uncertainty of around 6%.

1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/nuclear-parity-and-time-reversal-symmetry-violation-hgh-hg-201-molecule01816nas 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-violations01378nas a2200181 4500008004100000022001400041245010800055210006900163260000800232300001100240490000800251520073600259100002200995700002201017700001801039700001601057856012301073 2020 eng d a0021-960600aElectronic structure parameter of nuclear magnetic quadrupole moment interaction in metal monofluorides0 aElectronic structure parameter of nuclear magnetic quadrupole mo cNOV a1843060 v1533 a

The electronic structure parameter (W-M) of the nuclear magnetic quadrupole moment (MQM) interaction in numerous open-shell metal monofluorides (viz., MgF, CaF, SrF, BaF, RaF, and PbF) is computed in the fully relativistic coupled-cluster framework. The electron-correlation effects are found to be very important for the precise calculation of W-M in the studied molecular systems. The molecular MQM interaction parameter scales nearly as Z(2) in the alkaline earth metal monofluorides, where Z is the nuclear charge of metal. Our study identifies (RaF)-Ra-223 as a good candidate for the experimental search of the nuclear MQM, which can help unravel the physics beyond the standard model in the hadron sector of matter.

1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/electronic-structure-parameter-nuclear-magnetic-quadrupole-moment-interaction-metal01799nas 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-violation01866nas a2200205 4500008004100000022001400041245012500055210006900180260000800249300001100257490000800268520113700276100002001413700001801433700002201451700002201473700001801495700001601513856013101529 2020 eng d a0021-960600aRelativistic double-ionization equation-of-motion coupled-cluster method: application to low-lying doubly ionized states0 aRelativistic doubleionization equationofmotion coupledcluster me cMAR a1043020 v1523 a

This article deals with the extension of the relativistic double-ionization equation-of-motion coupled-cluster (DI-EOMCC) method [H. Pathak et al. Phys. Rev. A 90, 010501(R) (2014)] for the molecular systems. The Dirac-Coulomb Hamiltonian with four-component spinors is considered to take care of the relativistic effects. The implemented method is employed to compute a few low-lying doubly ionized states of noble gas atoms (Ar, Kr, Xe, and Rn) and Cl-2, Br-2, HBr, and HI. Additionally, we presented results with two intermediate schemes in the four-component relativistic DI-EOMCC framework to understand the role of electron correlation. The computed double ionization spectra for the atomic systems are compared with the values from the non-relativistic DI-EOMCC method with spin-orbit coupling [Z. Wang et al. J. Chem. Phys. 142, 144109 (2015)] and the values from the National Institute of Science and Technology (NIST) database. Our atomic results are found to be in good agreement with the NIST values. Furthermore, the obtained results for the molecular systems agree well with the available experimental values.

1 aPathak, Himadri1 aSasmal, Sudip1 aTalukdar, Kaushik1 aNayak, Malaya, K.1 aVeval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/relativistic-double-ionization-equation-motion-coupled-cluster-method-application-low-lying01561nas 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-investigation01793nas 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-physics01944nas 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