Month: August 2021

Dear Friends of UConn Physics

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As we approach the beginning of the 2021-22 school year, UConn is set for having classes in person again, students on campus, and our first taste of somewhat normal university life in a year and a half. Students, faculty, and staff are all required to be vaccinated, masks are required indoors, classrooms will be fully utilized and our labs are fully open once again. As with the rest of America, we are both excited to be coming back but nervous about what the future may hold.

The past year has been difficult for us, as with everyone else. We had been teaching most classes remotely, research labs have been open but running at reduced capacity, and our new physics building has been eerily quiet for the most part. What has surprised me the most has been the number of successes racked up within the department despite the trying times. Within this newsletter there are some great stories on some accomplishments, including the UConn contribution to the world-famous muon g-2 result, our part in the new world of multi-messenger astronomy, and Nora Berrah’s prestigious term as a Blaise Pascal International Scholar. This has also been one of our best years in winning external research funding, with particularly notable successes among our newer hires.

Another development over the past year is that the renovations of the new physics building have been largely completed and it is fully open, including the new Light Court in the center of our studio teaching labs. Physics now occupies the space that was formerly the Mathematics Building. Unfortunately, I cannot yet extend an open invitation to come visit, but I hope you will do so once the pandemic recedes and we are fully open. Given uncertainty in the health situation, we still cannot schedule major public events for this year. Our next Katzenstein Lecture is scheduled for September 23, 2022. The speaker will be Donna Strickland from the University of Waterloo (Canada), the 2018 Nobel Laureate for developing chirped pulse amplification – a key ingredient in today’s ultrafast laser technology. When the time comes, we will be sending out invitations. I hope many of you can attend the lecture, visit our building, and attend the following banquet.

I close by wishing all of us health and a successful return to a more normal kind of life over the next year.

 

Barry Wells

Physics Department Head

Physics alumnus Prof. Douglas Goodman and Professor Emeritus Winthrop Smith Featured in Online Peer Review Journal

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Prof. Emeritus Winthrop Smith and former student Prof. Douglas Goodman (Quinnipiac University) Edit Special Issue of Open Access Journal Atoms, on Low Energy Interactions between Ions and Ultracold Atoms

 The Special Issue of the online journal Atoms is a collection of current peer-reviewed articles by experts in the field of ultracold collisions and reactions involving ions and atoms co-trapped by electromagnetic fields in a common volume (a hybrid ion-neutral trap). Prof. Goodman, a recent UConn Ph.D. student of Prof. Smith (2015) who worked with hybrid traps for his dissertation, is now on the faculty of Quinnipiac University in Hamden, CT.

Prof. Smith’s research, on which he supervised four doctoral dissertations over the last few years, centers around the study of low-energy ion-neutral collisions. At long range, universal types of charge-induced polarization effects produce very large elastic, inelastic, reactive, and charge-transfer cross-sections leading to a high interaction probability between ions and neutral atoms at low temperature. The Special Issue articles highlight recent experimental and simulation work in this field and discuss the outlook for future developments.

Two of the manuscripts in this Special Issue explore recent advances in hybrid trap technology. The paper by Prof. Karpa explains the use of bichromatic optical dipole traps, which can be used instead of the previously developed hybrid rf ion trap and magneto-optic trap. This remarkable new technique avoids the use of rf fields and associated micromotion heating limitations and allows access to the long-sought quantum-dominated regime of interaction.

Karpa, L. Interactions of Ions and Ultracold Neutral Atom Ensembles inComposite Optical Dipole Traps: Developments and Perspectives. Atoms2021, 9(3), 39; https://doi.org/10.3390/atoms9030039 The manuscript included by Prof. Denschlag’s team, early practitioners of hybrid-trap ion-neutral studies, introduces a novel type of low-energy reaction. Denschlag’s group discusses the interaction between an atomic ion and an atom with a valence electron in a highly excited Rydberg state that reacts to yield a long-range atom-ion Rydberg molecule, with binding lengths up to the micrometer scale.Deiß, M.; Haze, S.; Hecker Denschlag, J. Long-Range Atom–Ion RydbergMolecule: A Novel Molecular Binding Mechanism. Atoms 2021, 9(2), 34;https://doi.org/10.3390/atoms9020034 https://www.mdpi.com/2218-2004/9/2/34

The remaining two manuscripts in this Special Issue address important phenomenology of rf Paul traps as they are used in ion-neutral interaction experiments. The paper by Prof. Blumel analyzes the properties of ion clouds loaded from a magneto-optical trap in a hybrid ion-neutral system. He develops theoretical predictions for optimal loading conditions for hybrid-trap experiments, which are supported by numerical simulations. Additionally, he predicts the existence of a new type of ion heating mechanism caused by the increase in Coulomb energy associated with each newly loaded ion within the existing ion-cloud volume.

Blümel, R. Loading a Paul Trap: Densities, Capacities, and Scaling inthe Saturation Regime. Atoms 2021, 9(1), 11; https://doi.org/10.3390/atoms9010011https://www.mdpi.com/2218-2004/9/1/11

Last, the manuscript by Prof. Rangwala’s group, numerically and analytically explores the benefits of using linear multipole rf traps for studying low-energy ion-neutral collisions, as opposed to the conventional quadrupole ion-trap configuration. Using new analyses of the heating effects, Rangwala’s group shows that the higher-order multipolar trap configurations reduce unwanted heating in the ion-neutral system. In doing so, they develop a methodology for comparing and optimizing hybrid trap designs.

Niranjan, M.; Prakash, A.; Rangwala, S. Analysis of Multipolar Linear

Paul Traps for Ion–Atom Ultracold Collision Experiments. Atoms 2021,

9(3), 38; https://www.mdpi.com/2218-2004/9/3/38

https://doi.org/10.3390/atoms9030038

New Faculty Hire-Dr. Anh-Thu Le

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The Physics Department welcomes our newest faculty member, Dr. Anh-Thu Le, although he prefers to be called simply AT. AT worked for many years at the well-known James R. Macdonald Laboratory, rising to the rank of Research Professor. He worked alongside a world-known theorist, Dr. Chii-Dong Lin. Dr. Le went on to become an Assistant Professor at Missouri University of Science and Technology before coming to UConn. Dr. Le is well-versed in current theoretical methods for exploring the interaction of ultrafast lasers with atoms and molecules. He has a strong overlap with the ultrafast AMO experimental programs at UConn and has collaborated with high-profile experimental groups.

Dr. Le has a thoroughly international and diverse background, having grown up in the Vietnamese countryside. His research career has taken him from Vietnam to the Republic of Belarus, Germany, Canada, and ultimately the US. This has left him with a lasting commitment to serving diverse populations, both in the classroom and in his research.

Professor Puckett’s Group Prepares New Measurements of “femtoscopic” Neutron Structure at Jefferson Lab

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UConn group on the floor of Hall A
The UConn group on the floor of Hall A during the SBS installation. From left to right: Postdoctoral Research Associate Dr. Eric Fuchey, Professor Andrew Puckett, and Graduate Research Assistants Provakar Datta and Sebastian Seeds. Click the image for a slideshow of additional installation photos and for more details about the experiment.

Professor Andrew Puckett’s research group is currently leading, as part of a collaboration of approximately 100 scientists from approximately 30 US and international institutions, the installation in Jefferson Lab’s Experimental Hall A of the first of a series of planned experiments known as the Super BigBite Spectrometer (SBS) Program, with beam to Hall A tentatively scheduled to begin in early September of 2021. Jefferson Lab, located in Newport News, Virginia, is a national user facility operated by the US Department of Energy, and is the world’s premiere laboratory for imaging the subatomic (and subnuclear) quark-gluon structure of protons, neutrons, and nuclei using its continuous, polarized electron beam. In addition to Professor Puckett, the UConn researchers involved in this effort are Postdoctoral Research Associate Eric Fuchey, and Graduate Research Assistants Provakar Datta and Sebastian Seeds. The first set of experiments in the SBS program, slated to run during Fall 2021, is focused on the measurement of neutron electromagnetic form factors at very large values of the momentum transfer Q2, which essentially probe the spatial distributions of electric charge and magnetism inside the neutron at very small distance scales of order 0.05-0.1 fm (1 fm = one femtometer = 10-15 m = 0.000 000 000 000 001 m), approximately 10-20 times smaller than the size of the proton and approximately 1 million times smaller than the size of a typical atom.

Electrons from Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF), with energies of up to 10 GeV (=10 billion electron-volts), will scatter elastically from protons and neutrons in a liquid deuterium target in Hall A. Scattered electrons will be detected in the BigBite Spectrometer, located on the left side of the beam, while the high-energy protons and neutrons recoiling from the “hard” collisions with the beam electrons will be detected in the SBS by the newly constructed Hadron Calorimeter (HCAL), located on the right side of the beam. The SBS dipole magnet will provide a small vertical deflection of the scattered protons, which allows HCAL to distinguish them from scattered neutrons, which are undeflected by the magnetic field, but produce otherwise identical signals in HCAL.

The first group of SBS experiments, collectively known as the “GMN run group”, will answer several important questions about the “femtoscopic” structure of the neutron, including:

  • What is the behavior of the neutron’s magnetic form factor at large momentum transfers? The SBS experiment will dramatically expand the Q2 reach of neutron magnetic form factor data compared to all previously existing measurements, from approximately 4 –> 14 (GeV/c)2. See original experiment proposal here.
  • How is the charge and magnetism of the proton shared among its “up” and “down” quark constituents as a function of Q2? The proton magnetic form factor has been measured over a much wider range of Q2 than the neutron, and combined proton and neutron measurements can be used to disentangle the contributions of “up” and “down” quarks (and diquark correlations) to the proton’s structure, under the assumption of charge symmetry of the strong interactions (see, e.g., https://inspirehep.net/literature/1812076)
  • How important and/or significant is the contribution of two-photon-exchange to elastic electron-neutron scattering? The first SBS experiment group will perform measurements of the electric/magnetic form factor ratio for the neutron using two different techniques known as “Rosenbluth Separation” and “Polarization Transfer”, at a Q2 where these two techniques have shown significant disagreement for the proton. Both measurements will be the first of their kind for the neutron at such large Q2 values (see, e.g., Polarization Transfer Proposal and Rosenbluth Separation Proposal)

The GMN run group will start in early September and run through the fall of 2021. The broader SBS program will continue in Hall A through at least 2023, and will drastically improve our understanding of the femtoscopic quark-gluon structure of protons, neutrons, and atomic nuclei. Professor Puckett’s research in the SBS and Hall A Collaborations is supported by the US Department of Energy, Office of Science, Office of Nuclear Physics. Stay tuned!