{"id":19,"date":"2016-05-18T00:34:15","date_gmt":"2016-05-18T00:34:15","guid":{"rendered":"https:\/\/physlabs.colostate.edu\/yostlabs\/?page_id=19"},"modified":"2025-06-11T16:59:43","modified_gmt":"2025-06-11T16:59:43","slug":"research","status":"publish","type":"page","link":"https:\/\/physlabs.colostate.edu\/yostlabs\/research\/","title":{"rendered":"Research"},"content":{"rendered":"

Overview<\/span><\/strong><\/h3>\n

The Yost Research Group is focused on low-energy tests of fundamental physics through two \u00a0experimental programs. \u00a0One is based on the high precision spectroscopy of simple atoms. \u00a0The other is a search for the interaction of photons in the absence of mediating matter.<\/p>\n

Precision Spectroscopy of Simple Atoms<\/strong><\/span><\/h3>\n

The Yost Research Group performs high precision spectroscopy of hydrogen, and occasionally other simple atoms. The study of simple atoms has been an extremely fruitful endeavor, catalyzing the development of quantum mechanics, quantum electrodynamics and even some nuclear physics. All of these advances occurred when discrepancies were found between the physical theories describing the atomic energy levels and the experimental data.<\/p>\n

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A major part of our research effort is the development of lasers with extremely precise frequencies. In fact, to perform competitive spectroscopic measurements, we will need to measure and control our laser frequency with at least 12 digits of precision. However, the precision of such an advanced laser source will not be transferred to an experimental measurement if the motion of the atoms is not well controlled. Therefore, we also investigate the motional control of atomic hydrogen with lasers. \u00a0A description of some of the research projects currently underway to help accomplish this goal are described below.<\/p>\n

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Laser Slowing of a Hydrogen Beam<\/span><\/span><\/p>\n

A common limitation to hydrogen spectroscopy experiments is the atomic velocity of the atomic sample at finite temperature. This introduces relativistic Doppler shifts, and transit-time broadening, inhibiting the precision with which hydrogen transitions can be measured.<\/p>\n

One way to reduce the temperature of the atoms is with laser cooling. Laser cooling involves tuning the frequency of a laser so that an atom will absorb radiation, but only if the direction of the photon opposes the motion of the atom. This technique has proved incredibly versatile and has become ubiquitous for the cooling of certain, heavy atomic species \u2013 mostly alkali and alkaline-earth atoms. Unfortunately, for hydrogen and anti-hydrogen, laser cooling requires Lyman-alpha radiation with a wavelength of 121 nm.<\/p>\n

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We are currently pursuing a different method to slow our hydrogen beam. \u00a0By tuning a laser close to a hydrogen transition, the atoms can experience a large force either towards or away from the high intensity region of the laser beam. \u00a0If a laser beam is reflected back onto itself, many regions of high and low-intensity are created \u00a0– an optical lattice. \u00a0By quickly turning on the optical lattice we are able to trap atoms in high or low intensity regions. \u00a0With electro-optics, we can control the motion of this lattice with high precision. \u00a0After the atoms are trapped, we then slow the lattice quickly to decelerate our hydrogen atoms. \u00a0Finally we turn the lattice off completely, producing a slow hydrogen beam. \u00a0The deceleration of an individual hydrogen atom can approach 1 billion g in this process.<\/p>\n

Supported by the NSF<\/em><\/p>\n

Optical Spectroscopy<\/span><\/strong><\/p>\n

Due to the simplicity of hydrogen, the theoretical determination of its energy levels is very precise. \u00a0However, there are two parameters — the proton charge radius and the Rydberg constant — which are needed to complete the theoretical description. \u00a0Therefore, measurements of two different transitions are needed to extract these parameters. \u00a0Any additional measurements can be used to check the consistency of the underlying theory.<\/p>\n

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There has been significant tension between the proton charge radius extracted from measurements in hydrogen and muonic hydrogen (a hydrogen atom where the electron has been replaced by a muon). \u00a0However, several new measurements in hydrogen have been consistent with the muonic result. CODATA2018<\/a><\/p>\n

This highlights the need for \u00a0independent hydrogen spectroscopy measurements if we hope to continue to test the hydrogen theory. \u00a0We have chosen to measure a certain transition — the 2S-8D — with high precision (a relative uncertainty of 2.6e-12). \u00a0<\/p>\n

Supported by the NSF and The NIST\u00a0Precision Measurement Grant<\/i><\/p>\n

RF Spectroscopy<\/span><\/strong><\/p>\n

In hydrogen, both the electron and the proton have magnetic moments (i.e. both act like tiny magnets) and these interact with each other to produce hyperfine structure. \u00a0The hyperfine structure of the ground state of hydrogen is the basis for the hydrogen maser — a very high performance frequency standard.<\/p>\n

We are now exciting our hydrogen beam to the 2S state — one of the first excited electronic states. \u00a0We will then study the hyperfine structure of this state. \u00a0By comparing \u00a0ground \u00a0and excited state hyperfine structure we can look for small deviations in the theoretical prediction. https:\/\/arxiv.org\/abs\/1005.4859<\/a><\/p>\n

Supported by the Center for Fundamental Physics (CFP)<\/a> Fundamental Physics Grant<\/em><\/p>\n

Search for Photon-Photon Interactions<\/strong><\/span><\/h3>\n

Through a generous grant through the Gordon and Betty Moore Foundation’s Experimental Physics Investigator Initiative, we are beginning a challenging experimental program aimed to search for the direct interaction of laser pulses in the absence of mediating matter. \u00a0This phenomena, which is called “Laser Induced Vacuum Birefringence,” has never been directly observed. \u00a0While it is an effect predicted by our most successful physical theory (quantum electrodynamics), it is possible that deviations from theory could exist, hinting at new physical phenomena.<\/p>\n

For this we will use optical cavities to store pulses of light (a pump pulse and a probe pulse) which will repeatedly collide. \u00a0In addition we will store a control pulse \u00a0which is timed to never interact with the pump pulse. \u00a0Then we will attempt to measure the small differences between the probe and control pulses by measuring the polarization of the pulses with photodiodes.<\/p>\n

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For more information on the experiment, please take a look at our recent publication in Physical Review Research:<\/p>\n

https:\/\/doi.org\/10.1103\/PhysRevResearch.7.023026<\/a><\/p>\n

https:\/\/arxiv.org\/abs\/2410.23198<\/a><\/p>\n

This work is supported by the Gordon and Betty Moore Foundation, GBMF12955, Grant DOI: 10.37807\/GBMF12955.<\/p>\n

https:\/\/www.moore.org\/grant-detail?grantId=GBMF12955<\/a><\/p>\n

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