Engaging new dimensions in nonlinear optical spectroscopy using auxiliary beams of light

By applying a sufficiently intense beam of off-resonant light, simultaneously with a conventional excitation source beam, the efficiencies of one- and two-photon absorption processes may be significantly modified. The nonlinear mechanism that is responsible, known as laser modified absorption, is fully described by a quantum electrodynamical analysis. The origin of the process, which involves stimulated forward Rayleigh-scattering of the auxiliary beam, relates to higher order terms which are secured by a time-dependent perturbation treatment. These terms, usually inconsequential when a single beam of light is present, become prominent under the secondary optical stimulus – even with levels of intensity that are moderate by today’s standards. Distinctive kinds of behaviour may be observed for chromophores fixed in a static arrangement, or for solution- or gas-phase molecules whose response is tempered by a rotational average of orientations. In each case the results exhibit an interplay of factors involving the beam polarisations and the molecular electronic response. Special attention is given to interesting metastable states that are symmetry forbidden by one- or two-photon absorption. Such states may be accessible, and thus become populated, on input of the auxiliary beam. For example, in the one-photon absorption case, terms arise that are more usually associated with three-photon processes, corresponding to very different selection rules. Other kinds of metastable state also arise in the two-photon process, and measuring the effect of applying the stimulus beam to absorbances of such character adds a new dimension to the information content of the associated spectroscopy. Finally, based on these novel forms of optical nonlinearity, there may be new possibilities for quantum non-demolition measurements

On the detection of characteristic optical emission from electronically coupled nanoemitters

Optical emission from an electronically coupled pair of nanoemitters is investigated, in a new theoretical development prompted by experimental work on oriented semiconductor polymer nanostructures. Three physically distinct mechanisms for photon emission by such a pair, positioned in the near-field, are identified: emission from a pairdelocalized exciton state, emission that engages electrodynamic coupling through quantum interference, and correlated photon emission from the two components of the pair. Each possibility is investigated, in detail, by examination of the emission signal via explicit coupling of the nanoemitter pair with a photodetector, enabling calculations to give predictive results in a form directly tailored for experiment. The analysis incorporates both near- and far-field properties (determined from the detector-pair displacement), so that the framework is applicable not only to a conventional remote detector, but also a near-field microscope setup. The results prove strongly dependent on geometry and selection rules. This work paves the way for a broader investigation of pairwise coupling effects in the optical emission from structured nanoemitter arrays

Great Diversity of Insect Floral Associates May Partially Explain Ecological Success of Poison Ivy (\u3ci\u3eToxicodendron Radicans\u3c/i\u3e Subsp. \u3ci\u3eNegundo\u3c/i\u3e [Greene] Gillis, Anacardiaceae)

Little is known about insect floral associates of poison ivy (Toxicodendron radicans, Anacardiaceae), despite the species’ ubiquity and importance in nature and society. Poison ivy’s pollination syndrome and results from prior studies suggest that the plant is not specialized for any particular pollinator type; however, a systematic survey exploring this hypothesis has been lacking. For this study, insect floral associates of Toxicodendron radicans subsp. negundo from a central Iowa site were observed during the flowering season of 2005. Thirty- seven distinct insect floral associates were observed: 8 coleopterans (beetles), 7 dipterans (flies), 2 hemipterans (true bugs), 19 hymenopterans (ants, bees, wasps), and 1 lepidopteran (butterfly). Hymenopterans appeared to be the most important contributors to poison ivy pollination on a per species basis; however, coleopterans and dipterans were also frequent associates. Poison ivy’s ability to utilize a diverse assemblage of insect pollinators may partially explain its ecological success in varied habitats

Public opinion in Poland\u27s transition to market economy

Public opinion research has changed dramatically in the last ten years in Poland, in terms of its methodology, scope, and role in political change. During the first Solidarity era (1980–81), the genie of public opinion was let out of the bottle, and even martial law could not entirely put it back. Public opinion polling in the 1980s became more sophisticated and more common, and began to tackle increasingly sensitive political issues. Public opinion came to play a role in the political process, and to give the Polish population a sense of its own purpose and values. It also revealed the depth of antipathy to the communist regime and leadership and, in doing so, further eroded the already fragile legitimacy of the regime. When, in the late 1980s, the regime realized it could not succeed at winning back the allegiance, or at least acquiescence, of the Polish population, it agreed to negotiate with the opposition. The result was the emergence of the first noncommunist regime in Eastern Europe

McCulloch at 200

March 6, 2019 marked the 200th anniversary of the Supreme Court’s issuance of its decision in McCulloch v. Maryland, upholding the constitutionality of the Second Bank of the United States, the successor to Alexander Hamilton’s national bank. McCulloch v. Maryland involved a constitutional challenge by the Second Bank of the United States to a Maryland tax on the banknotes issued by the Bank’s Baltimore branch. The tax was probably designed to raise the Second Bank’s cost of issuing loans and thereby disadvantage it relative to Maryland’s own state-chartered banks. Marshall’s opinion famously rejected the Jeffersonian strict-constructionist argument that implied powers are limited to those legislative means that are indispensably necessary to the viability of the enumerated power. Instead, Marshall concluded, Congress must have discretion to choose among any means convenient or well-adapted to implementing the government’s granted powers. After concluding that Congress had the power to create the Second Bank, the McCulloch opinion turned to the question of whether Maryland could tax it. Reasoning that the essence of federal supremacy is to remove all obstacles to federal government action within its sphere, Marshall concluded that states cannot tax operations of the federal government