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Fort Collins, CO, United States

Beyer A.,Max Planck Institute of Quantum Optics | Maisenbacher L.,Max Planck Institute of Quantum Optics | Matveev A.,Max Planck Institute of Quantum Optics | Pohl R.,Max Planck Institute of Quantum Optics | And 13 more authors.
Optics Express | Year: 2016

We present an active fiber-based retroreflector providing high quality phase-retracing anti-parallel Gaussian laser beams for precision spectroscopy of Doppler sensitive transitions. Our design is well-suited for a number of applications where implementing optical cavities is technically challenging and corner cubes fail to match the demanded requirements, most importantly retracing wavefronts and preservation of the laser polarization. To illustrate the performance of the system, we use it for spectroscopy of the 2S-4P transition in atomic hydrogen and demonstrate an average suppression of the first order Doppler shift to 4 parts in 106 of the full collinear shift. This high degree of cancellation combined with our cryogenic source of hydrogen atoms in the metastable 2S state is sufficient to enable determinations of the Rydberg constant and the proton charge radius with competitive uncertainties. Advantages over the usual Doppler cancellation based on corner cube type retroreflectors are discussed as well as an alternative method using a high finesse cavity. © 2016 Optical Society of America. Source

Rohringer N.,German Electron Synchrotron | Rohringer N.,Max Planck Institute for the Physics of Complex Systems | Ryan D.,Colorado Sate University | Purvis M.,Colorado Sate University | And 9 more authors.
Optics InfoBase Conference Papers | Year: 2011

The interaction of ultrashort high-intensity pulses from XFELs with neon gas at atmospheric pressures results in strong amplification of spontaneous emission of the neon K-α line and self-stimulated resonant Raman scattering in the x-ray regime. © 2011 Optical Society of America. Source

Weninger C.,Max Planck Institute for the Physics of Complex Systems | Weninger C.,Center for Free Electronic Laser Science | Purvis M.,Colorado Sate University | Ryan D.,Colorado Sate University | And 8 more authors.
Physical Review Letters | Year: 2013

We demonstrate strong stimulated inelastic x-ray scattering by resonantly exciting a dense gas target of neon with femtosecond, high-intensity x-ray pulses from an x-ray free-electron laser (XFEL). A small number of lower energy XFEL seed photons drive an avalanche of stimulated resonant inelastic x-ray scattering processes that amplify the Raman scattering signal by several orders of magnitude until it reaches saturation. Despite the large overall spectral width, the internal spiky structure of the XFEL spectrum determines the energy resolution of the scattering process in a statistical sense. This is demonstrated by observing a stochastic line shift of the inelastically scattered x-ray radiation. In conjunction with statistical methods, XFELs can be used for stimulated resonant inelastic x-ray scattering, with spectral resolution smaller than the natural width of the core-excited, intermediate state. © 2013 American Physical Society. Source

Murphy G.K.,Colorado Sate University | Hama N.,Colorado Sate University | Bedermann A.,Colorado Sate University | Dong P.,Colorado Sate University | And 6 more authors.
Organic Letters | Year: 2012

The carbocyclic core of the phomoidrides has been synthesized efficiently and in high yield. Key steps include a phenolic oxidation/intramolecular Diels-Alder sequence, tandem radical cyclization, and a late-stage Wharton fragmentation of a densely functionalized isotwistane skeleton. © 2012 American Chemical Society. Source

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