P<i>and/or</i>T violation

Sandars, P. G. H.

doi:10.1088/0031-8949/1993/t46/002

Cited by 18 publications

(18 citation statements)

References 34 publications

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“…We also draw attention to a long list of important and classic reviews that include or are fully devoted to EDMs and provide a number of different perspectives as well as the history of the motivations and context: Garwin and Lederman (1959), Shapiro (1968a,b), Sandars (1975Sandars ( , 1993, Ramsey (1982Ramsey ( , 1990a, Barr and Marciano (1989), Suzuki (1991, 1992), Commins (1993), Golub and Lamoreaux (1994), Khriplovich and Lamoreaux (1997), , Sandars (2001), Ginges and Flambaum (2004), Pospelov and Ritz (2005), Commins (2007), Roberts and Marciano (2009), Chupp (2010), Dubbers and Schmidt (2011), Engel et al (2013), Roberts et al (2015), and Yamanaka et al (2017).…”

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confidence: 99%

Electric dipole moments of atoms, molecules, nuclei, and particles

et al. 2019

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A permanent electric dipole moment (EDM) of a particle or system is a separation of charge along its angular-momentum axis and is a direct signal of T-violation and, assuming CPT symmetry, CP violation. For over sixty years EDMs have been studied, first as a signal of a parity-symmetry violation and then as a signal of CP violation that would clarify its role in nature and in theory. Contemporary motivations include the role that CP violation plays in explaining the cosmological matter-antimatter asymmetry and the search for new physics. Experiments on a variety of systems have become ever-more sensitive, but provide only upper limits on EDMs, and theory at several scales is crucial to interpret these limits. Nuclear theory provides connections from Standard-Model and Beyond-Standard-Model physics to the observable EDMs, and atomic and molecular theory reveal how CP-violation is manifest in these systems. EDM results in hadronic systems require that the Standard Model QCD parameter ofθ must be exceptionally small, which could be explained by the existence of axions -also a candidate darkmatter particle. Theoretical results on electroweak baryogenesis show that new physics is needed to explain the dominance of matter in the universe. Experimental and theoretical efforts continue to expand with new ideas and new questions, and this review provides a broad overview of theoretical motivations and interpretations as well as details about experimental techniques, experiments, and prospects. The intent is to provide specifics and context as this exciting field moves forward.

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confidence: 99%

Electric dipole moments of atoms, molecules, nuclei, and particles

et al. 2019

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“…The origin of this effect is not understood, though several particle physics theories have been proposed to account for it [3]. Here, we are concerned solely with the molecular physics implications of PT-odd symmetry violations, the phenomenology of which has been surveyed extensively by Sandars [5,6].…”

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Ab initioStudy ofPT-Odd Interactions in Thallium Fluoride

et al. 1997

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Ab initio Dirac-Fock calculations of PT-odd interactions in TlF are reported which employ large sets of kinetically balanced Gaussian basis functions. Revised estimates are reported of bounds on the value of the electric dipole moment of the proton, d p , the tensor-pseudotensor coupling constant, C T , and the Schiff moment of the 205 Tl nucleus, Q, based on analysis of existing experimental data. [S0031-9007(97)

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“…Copromoted active metallic sites on the edge of MoS 2 particles which may be relevant in hydrodesulphurization catalysts have also been identified in STM observations, again in an increasingly natural partnership with DFT computations [17]. Unless these results prove to be an example of the so-called materials gap faced by SPM, they could indicate that the small patches of MoS 2 seen in electron micrographs of these catalysts may be more significant than the more visibly striking, three-dimensional MoS 2 -coated particles also present [18]. The role of the SPM in catalyst studies will surely increase now that high pressure instruments with the capability of following dynamic events are available [19].…”

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confidence: 89%

Aiming to Satisfy the Demands of Catalyst Characterization and Spectroscopy

Howie

2005

MAM

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When properly interfaced to complementary approaches, the various techniques of advanced TEM and SEM are now accorded a crucial role in the realistic characterization of heterogeneous catalysts as used in industry [1]. With the pioneering development of environmental ETEM in the past few years, enormous strides have been made in extending these powerful methods to follow catalytic processes in the electron microscope [2,3]. Notable successes have included the elucidation of the active sites for butane oxidation in vanadium phosphate (VPO) catalysts [4], increased understanding of metal-support interactions [5,6], the role of the Ba promoter in Ru ammonia synthesis catalysts [7] and dynamic shape changes in the Cu particles used in methanol synthesis catalysts [8]. In combination with white-line EELS, changes of oxidation states in ceria-based automotive catalysts have been followed [9]. ETEM has also been extended to study hydrogenation and polymerization reactions in wet conditions and at the modest operating temperatures increasingly relevant environmentally [10]. Still better compromises between HREM and in-situ microscopy will be available with aberration-corrected lenses although the possibilities of higher beam current may be limited by specimen damage considerations.The pressure gap between these experiments and typical catalyst operating conditions is still enormous but may not be a serious problem in cases where the effect can be reliably addressed by recalculating the rate constants using standard thermodynamic theory [11]. Even when there is for example a pressure-induced change in surface adsorbate structure it may still be possible to make a comparison between high pressure operation and low pressure experiments carried out at reduced temperatures [12]. Nevertheless it is encouraging to note that there has been some success in adapting well established, photon-based spectroscopy techniques of molecular chemistry to the extreme conditions of pressure and temperature which are generally used. Thus recent reviews of true in-situ spectroscopy methods have tended to concentrate on IR spectroscopy, Raman spectroscopy, UV-VIS spectroscopy, electron paramagnetic resonance, NMR, Mossbauer spectroscopy, X-ray diffraction and EXAFS [13,14].Microscopists will be swift to note that, although some of these techniques allow characterization of active sites on an average basis, none of them convey full spatially-resolved information. Their enviable sensitivity to significant molecular properties at surfaces argues strongly for incorporating these facilities in our equipment. This would have the added advantage of giving microscopists a foot on one of the bridges across the pressure gap and thus providing at least further means of comparison between ETEM observations and the actual situation in a typical reactor. Identification of active sites and reaction pathways has also been demonstrated by close correlation of microscopy data with DFT computations despite doubts about theoretical handling of excited states [15]...

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Pand/orT violation

Cited by 18 publications

References 34 publications

Electric dipole moments of atoms, molecules, nuclei, and particles

Electric dipole moments of atoms, molecules, nuclei, and particles

Ab initioStudy ofPT-Odd Interactions in Thallium Fluoride

Aiming to Satisfy the Demands of Catalyst Characterization and Spectroscopy

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