1 Electro nic structure spectroscopy cold ion -atom elastic collision properties and photoassociation formation prediction of MgCs molecular ion

2025-04-28 0 0 2.39MB 49 页 10玖币

侵权投诉

Electronic structure, spectroscopy, cold ion-atom elastic collision properties and

photoassociation formation prediction of (MgCs)+ molecular ion

Mohamed Farjallah†a, DibyenduSardar†b, Bimalendu Debb, and Hamid Berrichea,c

aLaboratory of Interfaces and Advanced Materials, Faculty of Sciences of Monastir,

University of Monastir, 5019 Monastir, Tunisia

bSchool of Physical Sciences, Indian Association for the Cultivation of Science (IACS),

Jadavpur, Kolkata 700032, INDIA

cDepartment of Mathematics and Natural Sciences, School of Arts and Sciences, American

University of Ras Al Khaimah, RAK, P. O. Box 10021, UAE

†Author Contributions: M.F. and D.S. contributed equally to this manuscript.

Abstract

Studies on the interactions between an alkali atom and an alkaline earth ion at low energy are

important in the field of cold chemistry. In this paper we, extensively, study the structure,

interactions, and dynamics of (MgCs)+ molecular ion. We use an ab initio approach based on

the formalism of non-empirical pseudo-potential for Mg2+ and Cs+ cores, large Gaussian basis

sets and full valence configuration interaction. In this context, the (MgCs)+ cation is treated as

an effective two-electron system. Potential energy curves and their spectroscopic constants for

the ground and the first 41 excited states of 1,3Σ+, 1,3Π and 1,3Δ symmetries are determined.

Furthermore, we identify the avoided crossings between the electronic states of 1,3Σ+ and 1,3Π

symmetries. These crossings are related to the charge transfer process between the two ionic

limits Mg/Cs+ and Mg+/Cs. In addition, vibrational-level spacings, the transition and permanent

dipole moments are presented and analysed. Using the produced potential energy data, the

ground-state scattering wave functions and elastic cross sections for a wide range of energies

are performed. Furthermore, we predict the formation of translationally and rotationally cold

molecular ion (MgCs)+ in the ground state electronic potential energy by stimulated Raman

type process aided by ion-atom cold collision. In the low energy limit (< 1 mK), elastic

scattering cross sections exhibit Wigner law threshold behaviour; while in the high energy limit

the cross sections as a function of energy E go as E-1/3. A qualitative discussion about the

possibilities of forming the cold (MgCs)+ molecular ions by photoassociative spectroscopy is

presented.

Keywords: PseudoPotentials; Configuration Interaction; Potential Energy Curves;

Spectroscopic constants; Dipole Moments; Photoassociation; STIRAP.

I. Introduction

In the recent years, cold and ultra-cold molecules [1] have received considerable attention

owing to successful demonstrations of cooling and trapping of molecules [2] and their

importance in high-resolution spectroscopy [3]. Because of the characteristic of the long-range

ion–atom potential, cold ion–neutral collisions [4-6] are different from neutral–neutral and ion–

ion collisions. The long range ion–atom potential is described by −C4/r4, where C 4 = α q2

/(8πε0), with α being the static electric polarizability of the atom and r the ion–atom separation.

The scattering by this potential offers the primary channel for the exchange of energy between

the ions and atoms. Accordingly, the investigations of ion–neutral atom collisions at low energy

are very useful for the study of sympathetic cooling of atomic ion translational motion [7,8],

and to get a detailed control of the internal and external degrees of freedom of the molecular

ions [9]. In addition, interaction between the alkali atoms and alkaline earth ions (Be+, Mg+,

Sr+ and Ca+) offer opportunities for new developments in the field of ultra-cold quantum matter,

with a benefit of simpler and more reliable trapping compared to the neutral molecules.

Furthermore, a wealth of cold molecular ion species could be created, opening the way to a

rich chemistry at temperatures of a few mK or less [10]. Interactions between cold atoms and

ions are also relevant for important applications related to molecule formation in Bose–Einstein

condensates [11] and to quantum information. Photoassociation [12] and Feshbach resonance

tuning [13] are two main experimental techniques for a coherent production of ultracold

molecules from ultracold atoms.

Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-

earth ions Ca+, Sr+ and Ba+, were studied theoretically by Aymar et al [14] using effective core

potential based on quantum chemistry calculations of potential energy curves and transition

dipole moments of the related molecular ions. Furthermore, many experimental groups have

carried out experiments with various combinations of alkali atoms Rb and alkaline-earth atomic

ions: Rb atoms with Ca+ [15, 16] and Ba+ [17] ions. Moreover, recently, other groups have

studied the energy scaling of cold atom-atom-ion three-body recombination Ba++Rb+Rb in the

mK regime where a single 138Ba+ ion in a Paul trap is immersed into a cloud of

ultracold 87Rb atoms [18], and life and death of a cold BaRb+ molecule inside an ultracold

cloud of Rb atoms [19]. In addition, an optical dipole trap of Rb atoms has also been merged

in a Paul trap containing a few Ba+ atoms [20, 21].

Concerning MgH+, the first evidence of the formation of molecular MgH+ ions in a laser cooled

ion trap was reported by Baba and Waki [22], by introducing air into an Mg+ trap. Drewsen

and colleagues [23], who introduced a thermal gas H2or D2 into a laser cooled Mg+ trap creating

trapped MgH+ or MgD+ ions, carried out a more controlled experiment. Many other studies

concerning magnesium hydride investigated its photodissociation [24], branching ratios [25],

etc. . More recently, Aymar et al. [26] carried out a study of the electron structure of the MgH+

ionic molecule containing potential energy curves, transition and permanent dipole moment

spectra and static polarizabilities. Using an ab initio approach, Khemeri et al [27] performed a

study of the electronic properties of this molecule in the adiabatic representation.

About the MgLi+ molecule, Boldyrev et al. [28] determined its ground state spectroscopic

constants, using a split-valence basis MP2/6-311+G*. Pyykkö [29] used two methods: Hartree-

Fock (HF/6-31G *) and Møller-Plesset (MP) to calculate the equilibrium distance, well depth

and vibration frequency for the same states. More recently, Yufeng Gao and Tao Gao [30] used

the ab initio program package MOLPRO to determine the potential energy curves and the

permanent and transition dipole moments of the same molecules. They used the multi-reference

configuration interaction and valence full configuration interaction with large aug-cc-pCVQZ

basis sets taking into account the core–valence and scalar relativistic corrections.

A review of the scientific literature shows that experimental studies on (MgCs)+[31] cationic

molecule are practically absent. We noticed the existence of a recent single theoretical study

of (MgCs)+, where the authors Smialkowski and Tomza[32] reported only spectroscopic

constants for the ground state. Therefore, a more detailed and refined investigation of this

molecular system is desirable. Methods fundamentally similar to those used for the treatment

of MgLi+ molecule [33, 34] will be employed in the present study.

Several groups in the world have experimentally investigated atom-ion and cold molecular

diatomic mixtures. The list include Yb2+ [35], RbCa+ [36],CaBa+ [37], CaYb+ [38], RbYb+ [39],

LiCa+ [40], RbCa+ [41], NaCa+ [42], RbSr+ [43], LiYb+ [44],KCa+ [45], RbBa+ [46], Rb2+ [47-

49], BaRb+ [50], and Ca2+ [51]. Alkaline-earth ions are a common choice as advanced methods

for manipulation and detection of such ions have been developed over the years, opening

prospects for their applications in quantum simulation and computations[52-53]. Atom-ion

diatomic molecular systems can be produced via cold collision-induced charge-transfer

radiative association, light-induced photoassociation [54-58]or photoionization of ultra-cold

neutral molecules [49,51]. The effective core potential methods followed by CI and quantum

chemistry calculations are employed to calculate the potential energy curves and dipole

moments. In a very recent work [59] in our group, we investigated the electronic structure of

the five diatomic molecular ions composed of a Ca+ ion interacting with an alkali-metal atom:

CaX+ (X=Li, Na, K, Rb, Cs).

Very recently, Smialkowski and Tomza [32] theoretically investigated the ground state

electronic structure of single-charged molecular ions formed from two or three interacting

alkali-metal and alkaline-earth-metal atoms. They calculated ground-state electronic properties

of all diatomic AB+ and most of triatomic A2B+ molecular ions consisting of Li, Na, K, Rb, Cs,

Mg, Ca, Sr, Ba and Yb atoms. Smialkowski and Tomza [32] carried out a systematic study of

the electronic structure of MgX+ (X=Li, Na, K, Rb and Cs) ionic systems and presented the

potential energy curves and spectroscopic constants for their ground states.

Here we investigate the adiabatic potential energy curves for many electronic states of 1,3Σ+, 1,3Π

and 1,3Δ symmetries below the Mg2+Cs− asymptotic limit. Then, we extract from these curves the

spectroscopic constants (equilibrium distance Re, well depth De, electronic excitation energy Te,

frequency ωe, harmonicity constant ωexe, and rotational constant Be). In addition, vibrational-level

spacings and the dipole moments function are also presented and analyzed. By exploiting the ab-

initio potential energy data, we study elastic collisions between an alkali ion Cs+ and a neutral

alkaline earth atom Mg for the ground state collisional threshold. Besides that, we predict and

analyze the formation a of translationally and rotationally cold molecular ion by two-photon

incoherent Raman process in the presence of two applied lasers.

This paper is organized as follow. In section 2, the used methodology is briefly presented. We

report our results for (MgCs)+ and discuss them in Section 3. Finally, we conclude in section4.

II. Theory and Computational Details

In this section, we provide an insight into the technical details of the computational calculation

of the (MgCs)+ molecular ion. Numerous studies on heteronuclear alkaline-earth dimers such as

(MgK)+ [56], (BeLi)+ [60], (BeH)+ [61], (CaRb)+, (SrRb)+ and (BaRb)+ [41] have been performed.

Using the CIPSI package (Configuration Interaction by Perturbation of a multi-configuration wave

function Selected iteratively) of the Laboratoire de Physique et Chimie Quantique of Toulouse in

France [62]. The ionic system (MgCs)+ has 67 electrons. Therefore, we replaced the cores of the

Mg2+ (10 electrons) and Cs+ (54 electrons) with non- empirical pseudo-potentials proposed by

Barthelat and Durand [63-65]. Consequently, (MgCs)+ is treated as an effective two-electron

system, where the two valence electrons are moving in the field of the two cores. The pseudo-

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

10 玖币 0人已下载

立即下载

摘要：

1Electronicstructure,spectroscopy,coldion-atomelasticcollisionpropertiesandphotoassociationformationpredictionof(MgCs)+molecularionMohamedFarjallah†a,DibyenduSardar†b,BimalenduDebb,andHamidBerrichea,caLaboratoryofInterfacesandAdvancedMaterials,FacultyofSciencesofMonastir,UniversityofMonastir,5019Mon...

展开>> 收起<<

1 Electro nic structure spectroscopy cold ion -atom elastic collision properties and photoassociation formation prediction of MgCs molecular ion.pdf

共49页,预览5页

还剩页未读，继续阅读

声明：本站为文档C2C交易模式，即用户上传的文档直接被用户下载，本站只是中间服务平台，本站所有文档下载所得的收益归上传人(含作者)所有。玖贝云文库仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私，请立即通知玖贝云文库，我们立即给予删除！

1 Electro nic structure spectroscopy cold ion -atom elastic collision properties and photoassociation formation prediction of MgCs molecular ion

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

热门标签

举报选择: