01908nas a2200181 4500008004100000022001400041245007000055210006700125260000800192300001600200490000800216520132900224100002401553700001501577700001601592700001801608856010001626 2020 eng d a1089-563900aNegative ion resonance states: the fock-space coupled-cluster way0 aNegative ion resonance states the fockspace coupledcluster way cDEC a10407-104210 v1243 a

The negative ion resonance states, which are electron-molecule metastable compound states, play the most important role in free-electron controlled molecular reactions and low-energy free-electron-induced DNA damage. Their electronic structure is often only poorly described but crucial to an understanding of their reaction dynamics. One of the most important challenges to current electronic structure theory is the computation of negative ion resonance states. As a major step forward, coupled-cluster theories, which are well-known for their ability to produce the best approximate bound state electronic eigen solutions, are upgraded to offer the most accurate and effective approximations for negative ion resonance states. The existing Fock-space coupled-cluster (FSCC) and the equation-of-motion coupled-cluster (EOM-CC) approaches that compute bound states are redesigned for the direct and simultaneous determination of both the kinetic energy of the free electron at which the electron-molecule compound states are resonantly formed and the corresponding autodetachment decay rate of the electron from the metastable compound state. This Feature Article reviews the computation of negative ion resonances using the FSCC approach and, in passing, provides the highlights of the equivalent EOM-CC approach.

1 aBasumallick, Suhita1 aSajeev, Y.1 aPal, Sourav1 aVaval, Nayana uhttps://library.ncl.res.in/content/negative-ion-resonance-states-fock-space-coupled-cluster-way01675nas a2200241 4500008004100000022001400041245009400055210006900149260000900218490000800227520077000235653006901005653003901074653002001113653005701133653002001190100002401210700002701234700001601261700001801277700001601295856012201311 2020 eng d a0026-897600aShape resonance of sulphur dioxide anion excited states using the CAP-CIP-FSMRCCSD method0 aShape resonance of sulphur dioxide anion excited states using th cAUG 0 v1183 a

We have studied the shape resonance of excited states of sulphur dioxide (SO2) anion by using the correlated independent particle Fock space multi-reference coupled cluster (CAP-CIP-FSMRCCSD) method augmented by complex absorption potential. These resonant states have been trapped experimentally in recent years by electron collision. In particular, we have investigated e(-)-SO2 scattering and computed the negative-ion resonance states of the anion responsible for the two resonances around 4.45 and 6.56 eV and compared the results with the existing experimental observations. From the computational results using the CAP-CIP-FSMRCCSD method, it has been observed that both the resonances near 4.45 and 6.56 eV result from A(1) symmetries. [GRAPHICS] .

10aCAP augmented correlated independent particle (CAP-CIP-FSMRCCSD)10acomplex absorption potential (CAP)10acoupled cluster10aFock space multireference coupled cluster (FSMRCCSD)10ashape resonance1 aBasumallick, Suhita1 aBhattacharya, Sumantra1 aJana, Irina1 aVaval, Nayana1 aPal, Sourav uhttps://library.ncl.res.in/content/shape-resonance-sulphur-dioxide-anion-excited-states-using-cap-cip-fsmrccsd-method01585nas 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-based