Two-Photon Quantum Interference Polarization Spectroscopy: Measurements of Transition Matrix Elements in Atomic Rubidium

The estimation of the adequacy of theoretical calculations on the atomic structure requires availability of the precise experimental data on radiative properties of the atoms. Such data is also required in astronomy and some important areas of technology. The lack of precision of traditional spectroscopic studies of atom presents a fundamental obstacle for progress in these areas. For example, in atomic rubidium, the best precision of the traditional spectroscopic results is on the order of about 1 - 5%, which does not allow for clear assessment of the latest sophisticated theoretical calculations on atomic rubidium structure, with emphasis on different, in nature, effects. This situation is typical for atomic physics in general. The purpose of present study is obtaining the experimental data on the radiative properties of atomic rubidium with precision considerably higher than that of the traditional spectroscopic methods. This is accomplished by means of the two-photon quantum interference polarization spectroscopy. A two-photon polarization spectrum of the rubidium atom is obtained in the range of detunings -417 cm-1 to +99 cm-1 from atomic 5s2S1/2-5p 2P3/2-*8s2S1/2resonance. From analysis of the spectra the relativistic and many body effects on the wavefiinctions are revealed in the form of a uniquely defined parameter q = 2 x 10-6 (5) cm and an exact relation between parameters R and p which quantitatively describes the process: R = 1.01756 (57) + 81.466 (15) p where R is dimensionless and p is in cm. The obtained results can be thought of as specific experimentally established two-photon sum rules and can be used for testing the accuracy of the theoretical wavefiinctions. The experimental technique has important advantages comparing to some traditional spectroscopic methods and is essentially free of systematic effects

Safeguarding Imperiled Biodiversity and Evolutionary Processes in the Wallacea Center of Endemism

Wallacea—the meeting point between the Asian and Australian fauna—is one of the world's largest centers of endemism. Twenty-three million years of complex geological history have given rise to a living laboratory for the study of evolution and biodiversity, highly vulnerable to anthropogenic pressures. In the present article, we review the historic and contemporary processes shaping Wallacea's biodiversity and explore ways to conserve its unique ecosystems. Although remoteness has spared many Wallacean islands from the severe overexploitation that characterizes many tropical regions, industrial-scale expansion of agriculture, mining, aquaculture and fisheries is damaging terrestrial and aquatic ecosystems, denuding endemics from communities, and threatening a long-term legacy of impoverished human populations. An impending biodiversity catastrophe demands collaborative actions to improve community-based management, minimize environmental impacts, monitor threatened species, and reduce wildlife trade. Securing a positive future for Wallacea's imperiled ecosystems requires a fundamental shift away from managing marine and terrestrial realms independently

Safeguarding Imperiled Biodiversity and Evolutionary Processes in the Wallacea Center of Endemism

Wallacea—the meeting point between the Asian and Australian fauna—is one of the world's largest centers of endemism. Twenty-three million years of complex geological history have given rise to a living laboratory for the study of evolution and biodiversity, highly vulnerable to anthropogenic pressures. In the present article, we review the historic and contemporary processes shaping Wallacea's biodiversity and explore ways to conserve its unique ecosystems. Although remoteness has spared many Wallacean islands from the severe overexploitation that characterizes many tropical regions, industrial-scale expansion of agriculture, mining, aquaculture and fisheries is damaging terrestrial and aquatic ecosystems, denuding endemics from communities, and threatening a long-term legacy of impoverished human populations. An impending biodiversity catastrophe demands collaborative actions to improve community-based management, minimize environmental impacts, monitor threatened species, and reduce wildlife trade. Securing a positive future for Wallacea's imperiled ecosystems requires a fundamental shift away from managing marine and terrestrial realms independently

Measurement of the mass splittings between the b(b)over-bar chi(b,J)(1P) states

We present new measurements of photon energies and branching fractions for the radiative transitions Y(2S)→γχb(J=0,1,2)(1P). The masses of the χb states are determined from the measured radiative photon energies. The ratio of mass splittings between the χb substates, r≡(MJ=2-MJ=1)/(MJ=1-MJ=0), with M the χb mass, provides information on the nature of the bb̄ confining potential. We find r(1P)=0.542 ±0.022±0.024. This value is somewhat lower than the previous world average, but more consistent with the theoretical expectation that r(1P)<r(2P); i.e., that this mass splitting ratio is smaller for the χb(1P) states than for the χb(2P) states. ©1999 The American Physical Society