1,067 research outputs found
Temperature-dependent bulk viscosity of nitrogen gas determined from spontaneous Rayleigh-Brillouin scattering
Values for the bulk viscosity of molecular nitrogen gas (N2) were derived
from spontaneous Rayleigh-Brillouin (RB) scattering at ultraviolet wavelengths
(366.8 nm) and at a 90 degree scattering angle. Analysis of the scattering
profiles yield values showing a linear increasing trend in the temperature
interval from 255 K to 340 K. The present values, pertaining to hypersound
acoustics at frequencies in the GHz domain, are found to be in agreement with
results from acoustic attenuation experiments in N2 performed at MHz
frequencies
Towards European-wide Quality and Benchmarking of Open Educational Resources
Empowered by a multi-partner Consortium, MORIL will deliver high-quality Open Educational Resources (OER) with pedagogically-rich content, specifically designed and developed for distance learning. MORIL refers to "Multilingual Open Educational Resources for Independent Learning". It constitutes a New Generation of open resources, having a strong focus on development and delivery of quality-assured materials for off-campus target groups. MORIL is value added, as face-to-face didactics are not obligatory, contrary to on-campus education. Besides open offers, formal offers are fronted as well, establishing a transparent prospective learning path into higher education for those that seek recognition and/or certification. MORIL will provide a single European access point for lifelong open and flexible learning: a referatory to participating local repository portals. For courses of interest to domestic markets, universities can utilise multilingual versioning and localisation. Blending MORIL with leading edge quality assurance and benchmarking, truly provides the Consortium with a head start. European-wide quality and benchmarking is enabled by E-xcellence: a web-based instrument to assess the quality of e-learning in higher education. Although many instruments already exist, which cover the organisational and content-related quality assurance of higher education institutions and programmes, only few exist which have developed a focus on the parameters of quality assurance that govern e-learning and even fewer or none, have their focus on OER. E-xcellence as such being supplemented to MORIL, is to cater for open and accessible quality and benchmarking. MORIL is supported by the William and Flora Hewlett Foundation
Cavity Ring-down UV spectroscopy of the C-X electronic transition of CH
Rotationally resolved spectra of the C-X electronic system
of the CH radical were measured using cavity ring-down spectroscopy in
supersonically expanding, planar hydrocarbon plasma. The experimental
conditions allowed the study of highly excited rotational levels starting from
vibrationally excited states. Here we present some 200+ new or more accurately
recorded transitions in the 0-0, 1-1 and 2-2 vibronic bands in the ultraviolet
between 30900-32400 cm (324-309 nm). The resulting data, compared to
earlier measurements, allows for the determination of more precise molecular
constants for each vibrational state and therefore more precise equilibrium
values. From this an equilibrium bond length of 1.115798(17) \r{A} for the
C state is determined. A comprehensive list with observed
transitions for each band has been compiled from all available experimental
studies and constraints are placed on the predissociation lifetimes
Rayleigh-Brillouin scattering of carbon dioxide
The spectral lineshape of spontaneous Rayleigh-Brillouin scattering in CO2 is
studied in a range of pressures. The spectrum is influenced by the bulk
viscosity, which is a relaxation phenomenon involving the internal degrees of
freedom of the molecule. The associated relaxation rates can be compared to the
frequency shift of the scattered light, which demands precise measurements of
the spectral lineshape. We find the value of the bulk viscosity around 5.7 X
10^{-6} kg/(ms) for the range of pressures p= 2-4 bar and for conditions of
room temperature
B\,^1\Sigma^{+}_{u} and EF\,^{1}\Sigma^{+}_{g} level energies of D
Accurate absolute level energies of the B\,^1\Sigma^{+}_{u}, and
EF\,^{1}\Sigma^{+}_{g}, rovibrational quantum states of molecular
deuterium are derived by combining results from a Doppler-free two-photon laser
excitation study on several lines in the
(0,0) band, with results
from a Fourier-transform spectroscopic emission study on a low-pressure
hydrogen discharge. Level energy uncertainties as low as 0.0005 cm are
obtained for some low-lying E\,^{1}\Sigma^{+}_{g} inner-well rovibrational
levels, while uncertainties for higher-lying rovibrational levels and those of
the F\,^{1}\Sigma^{+}_{g} outer-well states are nominally 0.005 cm.
Level energies of B\,^1\Sigma^{+}_{u} rovibrational levels, for
and are determined at an accuracy of 0.001 cm. Computed
wavelengths of D Lyman transitions in the
B\,^1\Sigma^{+}_{u}-X\,^{1}\Sigma^{+}_{g} () bands are also tabulated
for future applications.Comment: appears in Journal of Molecular Spectroscopy (2014
Crisis and catharsis in atomic physics:Precise measurement of an atomic hydrogen transition resolves the proton size puzzle
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