Observation And Spectroscopy Of Ultracold Rydberg-atom Macrodimers

Recently molecules involving one or more Rydberg excitations have attracted considerable attention due to their unusual properties.Besides the exaggerated properties of the Rydberg atom,such as large size,long lifetime,and huge polarizability,they possess abundant vibrational states and exotic adiabatic potentials,which can be used to study vacuum fluctuations,quench ultracold collisions,and measure correlations in quantum gases.Two kinds of Rydberg molecules with distinct binding mechanisms have been observed: Rydberg-ground molecules and Rydberg-atom macrodimers.Rydberg-ground molecules,consisting of a Rydberg atom bound to one or more ground-state atoms via a low-energy electron scattering mechanism.The bond length of this type of molecule is ? 2n2,i.e.the Rydberg-atom radius or less.Rydberg-atom macrodimers consists of two Rydberg atoms that interact via long-range multipole interaction and have bond lengths ? 4n2.In this thesis,we calculate the adiabatic potentials of cesium n DJ Rydberg-atom pairs generated by electrostatic multipole interactions between Rydberg atoms.In experimental work,we prepare(n DJ)2 Rydberg–atom macrodimers using a two-color double-resonant photoassociation method.The measured spectra agree reasonably well with calculated molecular potentials and spectra.Main contents are as follows:1.We consider the selection and symmetries to calculate the adiabatic potential curves of cesium Rydberg-atom macrodimers using electrostatic multipole interaction model.We study the dependence of the adiabatic potentials on the size of the two-body basis sets used in the calculation,and on the maximal order,qmax,of the multipole terms included in the calculation.We determine the binding energies and lengths of the binding adiabatic potentials,investigate their scaling behaviors as a function of the effective principal quantum number,and discuss vibrational-state wave functions.We consider the applicability of the calculated potentials and excitation rates to an experimental scheme for preparing(n DJ)2 Rydberg-atom macrodimers using two-color double-resonant photoassociation.2.Rydberg-atom macrodimers are prepared by two-color photoassociation.The first color(laser pulse A)is set to resonantly excite Rydberg atom-A(seed atoms),and the second color(laser pulse B)is detuned relative to pulse A by an amount equal to the molecular binding energy.The molecules are measured by extraction of Rydberg-atom electric-field ionization and autoionization products,and ion detection.3.Cesium(62DJ)2 Rydberg-atom macrodimers are prepared by two-color photoassociation.Molecular spectra are compared with calculations of adiabatic molecular potentials to obtain the molecular binding energies.From the dependence of the molecular signal on the detection delay time,the lifetime of the molecules is estimated.4.We present distinct anti-blockade features of strongly interacting Rydberg atoms using a two-color excitation scheme.The first color(laser pulse A)resonantly excites a few seed Rydberg atoms,each of which establishes a blockade region due to the long-range multipole interactions.The second color(laser pulse B)is blue detuned relative to pulse A by an amount equal to the multipole-interaction-induced shifts of certain atoms to result in the anti-blockade effect.We investigate the dynamics of this anti-blockade excitation and simulate the experimental results using a multilevel two-body model.5.We calculate the adiabatic potentials of rubidium Rydberg-ion molecules using electrostatic multipole interaction model.The formalism is similar to the one used to describe Rydberg-atom macrodimers.We determine the binding energies and lengths of the binding adiabatic potentials and discuss vibrational-state wave functions.We consider two methods of producing Rydberg-ion molecules.One is a multi-stage process via a Rydberg-ground molecule.The other is a THz spectroscopy method via a Rydberg-atom macrodimer.We calculate the Rydberg-ground molecular potential considering the pseudopotential due to the scattering interaction between the Rydberg electron and ground-state atom.The innovations of this work:1.We calculate the adiabatic potentials of cesium(n DJ)2 Rydberg macrodimers using the model of long-range multipole including dipole,quadrupole,octupole and hexadecupole interactions.2.The Rydberg-atom macrodimers are photo-associated in two resonant steps,leading to a greatly enhanced excitation rate of deeply bound molecules.3.We present electrostatic multipole interaction model to calculate the adiabatic potentials of rubidium Rydberg-ion molecules.We consider two methods of producing such molecules,one is a multi-stage process via a Rydberg-ground molecule,and the other is a THz spectroscopy method via a Rydberg-Rydberg molecule.