In this article we study the effects of higher body excitations in the relativistic CC calculations for atoms and ions with one valence electron using Fock-space CCSD, CCSD(T) and its unitary variants. The present study demonstrates that CCSD(T) estimates the ionization potentials (IPs) and the valence electron removal energies quite accurately for alkali atoms and singly ionized alkaline earth ions, but yields unphysical energy levels for atoms and/or ions with partially filled sub-shell like C II. We further demonstrate that the higher body excitation effects can be incorporated more effectively through the unitary coupled cluster theory (UCC) compared to the CCSD(T) method.
We present a cost-effective treatment of the triple excitation amplitudes in the time-dependent optimized coupled-cluster (TD-OCC) framework called TD-OCCDT(4) for studying intense laser-driven multielectron dynamics. It considers triple excitation amplitudes correct up to fourth-order in many-body perturbation theory and achieves a computational scaling of O(N7), with N being the number of active orbital functions. This method is applied to the electron dynamics in Ne and Ar atoms exposed to an intense near-infrared laser pulse with various intensities. We benchmark our results against the ti…
Triple excitations in perturbed relativistic coupled-cluster theory and Electric dipole polarizability of groupIIB elements
我们用微扰相对论耦合团簇(PRCC)理论计算了Zn、Cd和Hg的电偶极极化率$α$。计算是使用Dirac-Coulomb-Breit哈密顿量和Uehling势结合真空极化修正完成的。在PRCC理论中,三重激发是微扰的,而在未微扰区,三重激发是非微扰的。我们的结果$α$,所有三个元素,是在极好的协议与实验数据。结果的另一个亮点是Breit相互作用的轨道能量修正。在文献中,我们只能得到Hg {E。Lindroth等人,J. Phys. B 22,2447(1989)},并且与我们的结果几乎完全匹配。我们还提出了团簇振幅的线性化方程,包括三重激发,角因子。
We carried out calculations of the energies, hyperfine structure constants and electric-dipole transiton amplitudes for the low-lying states of Ba+ in the framework of the relativistic linearized coupled-cluster single double (LCCSD) and coupled-cluster single double (valence) triple (CCSDvT) methods. Taking into account that an iterative inclusion of the valence triples into consideration is a complicated and computationally demanding process we study the effects of computational restriction on the final results. We also present a detailed study of various corrections to all calculated proper…
Investigating Role of Electron Correlation Effects via Triple Excitations for Precise Evaluation of Energies and Hyperfine Structure Constants in $^{23}$Na
Physical Research Laboratory(物理研究实验室);Indian Institute of Technology Gandhinagar(甘地纳加尔印度理工学院)
Rydberg EIT-based microwave sensing has limited microwave-to-optical conversion bandwidth due to fundamental limitation in the optical pumping rate to its dark state. We demonstrate a parametric six-wave mixing of optical probe and coupling fields driving the atoms to a Rydberg state via two-photon excitation and two microwave fields with frequency offset of $δ$ driving the Rydberg-Rydberg transition in thermal atomic vapor. Microwave-to-optical conversion bandwidth of $17$ MHz is achieved in the present experiment which is limited by the available coupling power. Further theoretical investiga…
Ordered atomic arrays trapped in the vicinity of nanoscale waveguides offer original light-matter interfaces, with applications to quantum information and quantum non-linear optics. Here, we study the decay dynamics of a single collective atomic excitation coupled to a waveguide in different configurations. The atoms are arranged as a linear array and only a segment of them is excited to a superradiant mode and emits light into the waveguide. Additional atomic chains placed on one or both sides play a passive role, either reflecting or absorbing this emission. We show that when varying the geo…
Atom-waveguide interface mediates significant and long-range light-matter interactions through the guided modes. In this one-dimensional system, we theoretically investigate the excitation localization of multiple atomic excitations under strong position disorders. Deep in the localization side, we obtain the time evolutions of quantum correlations via Kubo cumulant expansions, which arise initially and become finite and leveled afterward, overtaking the ones without disorders. This indicates two distinct regimes in time: before the onset of excitation localization, the disorders engage the di…
Investigating Roles of Triple Excitations for High-precision Determination of Clock Properties of Alkaline Earth Metal Singly Charged Ions
Atomic, Molecular and Optical Physics Division, Physical Research Laboratory(物理研究实验室原子、分子与光学物理分部);Indian Institute of Technology Gandhinagar(甘地纳加尔印度理工学院)