Jamie MacLennan - Academia.edu (original) (raw)

Papers by Jamie MacLennan

In this dissertation, I explore several aspects of Rydberg physics with laser spectroscopy. The e... more In this dissertation, I explore several aspects of Rydberg physics with laser spectroscopy. The experiments center around the use of a very deep, cavity-generated, one-dimensional optical lattice in a cold atom sample. The optical lattice produces elongated clouds of dense, cold atoms via dipole trapping and is able to generate extreme light shifts in the atoms due to its high intensity. I describe experiments which may be divided into two main classes. In the first, I use the dipole trap to prepare a dense sample of atoms for photoassociation of Rb atom pairs into diatomic Rydberg molecules. The Rydberg molecules are formed by low-energy scattering of the Rydberg electron of one atom from the other atom, which is a ground-state atom. This novel binding mechanism also has relevance for chemical physics. I present binding energy measurements for eight different cases of Rydberg molecules. The binding energies reveal information about electron-atom collisions, such as their scattering...

New Journal of Physics, 2021

We develop a formalism for photoionization (PI) and potential energy curves (PECs) of Rydberg ato... more We develop a formalism for photoionization (PI) and potential energy curves (PECs) of Rydberg atoms in ponderomotive optical lattices and apply it to examples covering several regimes of the optical-lattice depth. The effect of lattice-induced PI on Rydberg-atom lifetime ranges from noticeable to highly dominant when compared with natural decay. The PI behavior is governed by the generally rapid decrease of the PI cross sections as a function of angular-momentum (ℓ), lattice-induced ℓ-mixing across the optical-lattice PECs, and interference of PI transition amplitudes from the lattice-mixed into free-electron states. In GHz-deep lattices, ℓ-mixing leads to a rich PEC structure, and the significant low-ℓ PI cross sections are distributed over many lattice-mixed Rydberg states. In lattices less than several tens-of-MHz deep, atoms on low-ℓ PECs are essentially ℓ-mixing-free and maintain large PI rates, while atoms on high-ℓ PECs trend towards being PI-free. Characterization of PI in G...

Bulletin of the American Physical Society, 2016

Bulletin of the American Physical Society, 2017

Submitted for the DAMOP17 Meeting of The American Physical Society Measurement of nD Rydberg-grou... more Submitted for the DAMOP17 Meeting of The American Physical Society Measurement of nD Rydberg-ground molecules in Rb JAMIE MACLENNAN, GEORG RAITHEL, University of Michigan-We experimentally measure the energies of several Rydberg-ground molecular bound states in Rb(nD + 5S 1/2), including vibrationally excited states. Because these molecular states arise from the scattering interaction of a Rydberg electron with a ground-state atom, their measurement allows an estimate of scattering lengths. Photoassociation out of an optical dipole trap facilitates our observation of molecules of relatively low principal quantum numbers, leading to good resolution of the bound-energy measurements. The study further addresses hyperfine-mixed singlet-triplet states.

The US Army Ground Vehicle Programs use various drive cycles for testing and validation of new ve... more The US Army Ground Vehicle Programs use various drive cycles for testing and validation of new vehicle systems and models. These cycles have traditionally been characterized by run speed, number of stops, and terrain profile. For the sake of powertrain analysis, there have been a number of additional metrics proposed for characterization of such drive cycles in the context of fuel economy evaluation. This paper examines several metrics related to fuel economy, comparing standard Army test circuits, simulated drive cycles, and commercially standardized drive cycles. By comparing these cycles and identifying key metrics, we can develop better testing plans and bench cycles for technology evaluation. Field data from a mountainous region shows substantial variability that is not fully captured by current test cycles. Kinetic intensity is able to differentiate between the human in the loop scenarios, with values higher in simulated cycles than in field data. However, number of stops rema...

Bulletin of the American Physical Society, 2018

Abstract: Over the past several years, legged mechanisms have shown remarkable progress towards p... more Abstract: Over the past several years, legged mechanisms have shown remarkable progress towards practicality. The need now is for efficient means of controlling these mechanisms. In previous papers, we have found the optimal switching curve for controlling a simplified ...

Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Bulletin of the American Physical Society, Jun 3, 2021

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, 2020

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, 2020

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, May 1, 2018

Collisions with background atoms are known to induce a significant shift in the frequency of stat... more Collisions with background atoms are known to induce a significant shift in the frequency of state-of-the-art optical atomic clocks and contribute to state decoherence in cold atom experiments. The effects of these collisions can be quantified by measuring their cross sections. We experimentally measured the collision cross section between ^88Sr-N_2 in a Magneto-Optical Trap (MOT). The measurement was carried out by monitoring the atom number loss rate as a function of background pressure of N_2 and the cross section thus obtained was 8.1(4)× 10^-18 m^2. The measured collision cross section has been utilized for the determination of C_6 coefficient of the ground state (^1S_0) of ^88Sr atom, which can be useful to estimate the relative frequency shift in the clock transition. We also estimate the loss rate induced by the combined effect of the decay of atoms in the long-lived ^3P_0 state and temperature-induced atomic losses from the capture volume of the MOT. We find that the contri...

We observe long-range ^85Rb and ^87Rb (24D+5S_1/2) Rydberg molecules for eight different spin cou... more We observe long-range ^85Rb and ^87Rb (24D+5S_1/2) Rydberg molecules for eight different spin couplings, with binding energies up to 440 MHz and sub-percent relative uncertainty. Isotopic effects of the molecular binding energies arise from the different masses and nuclear spins. Because the vibrational states involve different spin configurations and cover a wide range of internuclear separations, the states have different dependencies on the s-wave and p-wave scattering phase shifts for singlet and triplet scattering. Fitting the spectroscopic data, we comprehensively determine all four scattering length functions over the relevant energy range as well as the zero-energy scattering lengths of the two s-wave channels. Our unusually high temperature and low density (180 μK, 1 × 10^11 cm^-3) suggest that the molecule excitation occurs through photoassisted collisions.

molecules and circular Rydberg states in cold atom clouds by

arXiv: Atomic Physics, 2019

Obtaining a large momentum difference between matter wave-packets traversing the two paths in an ... more Obtaining a large momentum difference between matter wave-packets traversing the two paths in an atom interferometer while preserving the phase coherence is a challenge. We experimentally investigate a pulse sequence in which this momentum difference is obtained by using the matter-wave Talbot effect as an alternative to the conventional light-pulse atom interferometers. An ensemble of coherent atoms (Bose-Einstein condensate) is exposed to a periodic sequence of 2N2N2N standing wave pulses of far-detuned light. The first set of NNN pulses in the sequence produces multiple wavepackets with momentum difference up to 28 hbark\hbar khbark (at N=5N=5N=5), by virtue of Talbot resonance. The second set of NNN pulses reverses the momentum transfer and allows the wavepackets to retrace the path and interfere to retrieve the initial wavepacket. We observe that the degree of reversal and thus the practical performance of the interferometer is sensitive to the initial momentum width of the atomic ensemble.

Bulletin of the American Physical Society, 2016

48109-Radiation guiding through a dense, elongated cold-atom cloud in a deep optical lattice crea... more 48109-Radiation guiding through a dense, elongated cold-atom cloud in a deep optical lattice created by an in-vacuum cavity has been experimentally observed [1]. When atoms are loaded into the optical lattice, a cylindrically symmetric depletion zone surrounding the lattice location is created. This variation in atomic density gives rise to a position-dependent index of refraction which allows for a probe beam properly coupled into the atomic cloud to be guided through it. For a Hermite-Gaussian mode (HG 00), this mini fiber exhibits a transmission pattern consisting of a central feature and multiple concentric rings around it, with higher cavity modes also being accessible in the current experimental setup. Simulations that look to properly model these features are presented. This form of radiation guiding can be useful for Rydberg polariton and EIT experiments, where the atomic fiber would guide one or more trains of single-photon pulses, depending on the cavity mode [2]. [1] Yun-Jhih Chen, Stefan Zigo, and Raithel, G. "Atom trapping and spectroscopy in cavity-generated optical potentials."

Journal of Physics B: Atomic, Molecular and Optical Physics, 2020

This experimental work demonstrates the importance of finite-width effects in the evolution of a ... more This experimental work demonstrates the importance of finite-width effects in the evolution of a quantum system, where the results deviate considerably from the plane wave approximation even for an initial state with a very narrow momentum width i.e a Bose–Einstein condensate. The system under consideration is an atom optics δ-kicked rotor for which a fidelity based measurement has been proposed to possess a rapid scaling of sensitivity (N −3) with pulse number N. Although attractive, we demonstrate that this scaling does not hold in the regime where the momentum selectivity of the pulse sequence becomes significantly smaller than the momentum width of the initial state. Additionally, the momentum distribution post kicking shows a lattice-phase dependent intra-order and inter-order asymmetry in the diffracted orders. The intra-order asymmetry, in which no net momentum current is present, is a previously unreported type of effect. For a two pulse case, the inter-order asymmetry signa...

In this dissertation, I explore several aspects of Rydberg physics with laser spectroscopy. The e... more In this dissertation, I explore several aspects of Rydberg physics with laser spectroscopy. The experiments center around the use of a very deep, cavity-generated, one-dimensional optical lattice in a cold atom sample. The optical lattice produces elongated clouds of dense, cold atoms via dipole trapping and is able to generate extreme light shifts in the atoms due to its high intensity. I describe experiments which may be divided into two main classes. In the first, I use the dipole trap to prepare a dense sample of atoms for photoassociation of Rb atom pairs into diatomic Rydberg molecules. The Rydberg molecules are formed by low-energy scattering of the Rydberg electron of one atom from the other atom, which is a ground-state atom. This novel binding mechanism also has relevance for chemical physics. I present binding energy measurements for eight different cases of Rydberg molecules. The binding energies reveal information about electron-atom collisions, such as their scattering...

New Journal of Physics, 2021

We develop a formalism for photoionization (PI) and potential energy curves (PECs) of Rydberg ato... more We develop a formalism for photoionization (PI) and potential energy curves (PECs) of Rydberg atoms in ponderomotive optical lattices and apply it to examples covering several regimes of the optical-lattice depth. The effect of lattice-induced PI on Rydberg-atom lifetime ranges from noticeable to highly dominant when compared with natural decay. The PI behavior is governed by the generally rapid decrease of the PI cross sections as a function of angular-momentum (ℓ), lattice-induced ℓ-mixing across the optical-lattice PECs, and interference of PI transition amplitudes from the lattice-mixed into free-electron states. In GHz-deep lattices, ℓ-mixing leads to a rich PEC structure, and the significant low-ℓ PI cross sections are distributed over many lattice-mixed Rydberg states. In lattices less than several tens-of-MHz deep, atoms on low-ℓ PECs are essentially ℓ-mixing-free and maintain large PI rates, while atoms on high-ℓ PECs trend towards being PI-free. Characterization of PI in G...

Bulletin of the American Physical Society, 2016

Bulletin of the American Physical Society, 2017

Submitted for the DAMOP17 Meeting of The American Physical Society Measurement of nD Rydberg-grou... more Submitted for the DAMOP17 Meeting of The American Physical Society Measurement of nD Rydberg-ground molecules in Rb JAMIE MACLENNAN, GEORG RAITHEL, University of Michigan-We experimentally measure the energies of several Rydberg-ground molecular bound states in Rb(nD + 5S 1/2), including vibrationally excited states. Because these molecular states arise from the scattering interaction of a Rydberg electron with a ground-state atom, their measurement allows an estimate of scattering lengths. Photoassociation out of an optical dipole trap facilitates our observation of molecules of relatively low principal quantum numbers, leading to good resolution of the bound-energy measurements. The study further addresses hyperfine-mixed singlet-triplet states.

The US Army Ground Vehicle Programs use various drive cycles for testing and validation of new ve... more The US Army Ground Vehicle Programs use various drive cycles for testing and validation of new vehicle systems and models. These cycles have traditionally been characterized by run speed, number of stops, and terrain profile. For the sake of powertrain analysis, there have been a number of additional metrics proposed for characterization of such drive cycles in the context of fuel economy evaluation. This paper examines several metrics related to fuel economy, comparing standard Army test circuits, simulated drive cycles, and commercially standardized drive cycles. By comparing these cycles and identifying key metrics, we can develop better testing plans and bench cycles for technology evaluation. Field data from a mountainous region shows substantial variability that is not fully captured by current test cycles. Kinetic intensity is able to differentiate between the human in the loop scenarios, with values higher in simulated cycles than in field data. However, number of stops rema...

Bulletin of the American Physical Society, 2018

Abstract: Over the past several years, legged mechanisms have shown remarkable progress towards p... more Abstract: Over the past several years, legged mechanisms have shown remarkable progress towards practicality. The need now is for efficient means of controlling these mechanisms. In previous papers, we have found the optimal switching curve for controlling a simplified ...

Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Bulletin of the American Physical Society, Jun 3, 2021

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, 2020

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, 2020

APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, May 1, 2018

Collisions with background atoms are known to induce a significant shift in the frequency of stat... more Collisions with background atoms are known to induce a significant shift in the frequency of state-of-the-art optical atomic clocks and contribute to state decoherence in cold atom experiments. The effects of these collisions can be quantified by measuring their cross sections. We experimentally measured the collision cross section between ^88Sr-N_2 in a Magneto-Optical Trap (MOT). The measurement was carried out by monitoring the atom number loss rate as a function of background pressure of N_2 and the cross section thus obtained was 8.1(4)× 10^-18 m^2. The measured collision cross section has been utilized for the determination of C_6 coefficient of the ground state (^1S_0) of ^88Sr atom, which can be useful to estimate the relative frequency shift in the clock transition. We also estimate the loss rate induced by the combined effect of the decay of atoms in the long-lived ^3P_0 state and temperature-induced atomic losses from the capture volume of the MOT. We find that the contri...

We observe long-range ^85Rb and ^87Rb (24D+5S_1/2) Rydberg molecules for eight different spin cou... more We observe long-range ^85Rb and ^87Rb (24D+5S_1/2) Rydberg molecules for eight different spin couplings, with binding energies up to 440 MHz and sub-percent relative uncertainty. Isotopic effects of the molecular binding energies arise from the different masses and nuclear spins. Because the vibrational states involve different spin configurations and cover a wide range of internuclear separations, the states have different dependencies on the s-wave and p-wave scattering phase shifts for singlet and triplet scattering. Fitting the spectroscopic data, we comprehensively determine all four scattering length functions over the relevant energy range as well as the zero-energy scattering lengths of the two s-wave channels. Our unusually high temperature and low density (180 μK, 1 × 10^11 cm^-3) suggest that the molecule excitation occurs through photoassisted collisions.

molecules and circular Rydberg states in cold atom clouds by

arXiv: Atomic Physics, 2019

Obtaining a large momentum difference between matter wave-packets traversing the two paths in an ... more Obtaining a large momentum difference between matter wave-packets traversing the two paths in an atom interferometer while preserving the phase coherence is a challenge. We experimentally investigate a pulse sequence in which this momentum difference is obtained by using the matter-wave Talbot effect as an alternative to the conventional light-pulse atom interferometers. An ensemble of coherent atoms (Bose-Einstein condensate) is exposed to a periodic sequence of 2N2N2N standing wave pulses of far-detuned light. The first set of NNN pulses in the sequence produces multiple wavepackets with momentum difference up to 28 hbark\hbar khbark (at N=5N=5N=5), by virtue of Talbot resonance. The second set of NNN pulses reverses the momentum transfer and allows the wavepackets to retrace the path and interfere to retrieve the initial wavepacket. We observe that the degree of reversal and thus the practical performance of the interferometer is sensitive to the initial momentum width of the atomic ensemble.

Bulletin of the American Physical Society, 2016

48109-Radiation guiding through a dense, elongated cold-atom cloud in a deep optical lattice crea... more 48109-Radiation guiding through a dense, elongated cold-atom cloud in a deep optical lattice created by an in-vacuum cavity has been experimentally observed [1]. When atoms are loaded into the optical lattice, a cylindrically symmetric depletion zone surrounding the lattice location is created. This variation in atomic density gives rise to a position-dependent index of refraction which allows for a probe beam properly coupled into the atomic cloud to be guided through it. For a Hermite-Gaussian mode (HG 00), this mini fiber exhibits a transmission pattern consisting of a central feature and multiple concentric rings around it, with higher cavity modes also being accessible in the current experimental setup. Simulations that look to properly model these features are presented. This form of radiation guiding can be useful for Rydberg polariton and EIT experiments, where the atomic fiber would guide one or more trains of single-photon pulses, depending on the cavity mode [2]. [1] Yun-Jhih Chen, Stefan Zigo, and Raithel, G. "Atom trapping and spectroscopy in cavity-generated optical potentials."

Journal of Physics B: Atomic, Molecular and Optical Physics, 2020

This experimental work demonstrates the importance of finite-width effects in the evolution of a ... more This experimental work demonstrates the importance of finite-width effects in the evolution of a quantum system, where the results deviate considerably from the plane wave approximation even for an initial state with a very narrow momentum width i.e a Bose–Einstein condensate. The system under consideration is an atom optics δ-kicked rotor for which a fidelity based measurement has been proposed to possess a rapid scaling of sensitivity (N −3) with pulse number N. Although attractive, we demonstrate that this scaling does not hold in the regime where the momentum selectivity of the pulse sequence becomes significantly smaller than the momentum width of the initial state. Additionally, the momentum distribution post kicking shows a lattice-phase dependent intra-order and inter-order asymmetry in the diffracted orders. The intra-order asymmetry, in which no net momentum current is present, is a previously unreported type of effect. For a two pulse case, the inter-order asymmetry signa...