[en] A review of some of the aims and techniques of laser spectroscopy is presented. The basic theory of the hyperfine structure and isotope shifts observed in atomic spectral lines is discussed. The king plot technique for the study of isotope shift data, obtained using laser spectroscopy, is examined. Using two tunable dye lasers in heterodyne spectroscopy, hyperfine structure splittings in sodium and samarium and isotope shifts in samarium spectral lines have been measured. A semi quantitative study of samarium spectral lines was also undertaken using a single tunable dye laser which was tuned through resonances in an atomic beam to produce resonant scattering spectra. (U.K.)

[en] Securing access to affordable, reliable and clean energy is one of the great challenges facing governments around the world. The Australian Government is committed to ensuring the security of Australia's domestic energy systems as a fundamental part of Australia's social and economic prosperity. Energy in Australia 2011 is a key reference for anyone with an interest in Australian energy issues. It provides a detailed overview of energy in Australia from production to consumption, and serves as a useful resource to inform industry, government and the community.

[en] Measurements of the even-even isotope shifts in seven Sm spectral lines made using tunable dye laser heterodyne spectroscopy are presented. Anomalies in the isotope shifts in the level at 19 192 cm^-1 in the Sm I spectrum reported previously have been confirmed to within experimental uncertainty by data from the line at 564.75 nm which couples to that level. Results from the line at 565.28 nm show equal and opposite deviations, from straight lines fitted through King plots, to the anomalies produced by the data from the 19 192 cm^-1 level. (author)

[en] Laser heterodyne spectroscopic measurements of the optical isotope shifts between the naturally occurring even-even isotopes of samarium have been made in eleven lines of the Sm I spectrum. These have been used to study the J-dependent differences between the isotope shifts of the levels of the ground term which were recently discovered by Bauche and co-workers (J. Phys. B.; 10:2049 (1977)). The present work confirms the experimental results of these authors and, by including more than one isotope pair, allows the field and mass shift contributions to the total J dependence to be separated from each other. It is found that the proportion of the observed J dependence due to the field shift is at least four times that due to the mass shift: these results are not quite in accord with the theoretical results of Bauche et al. (author)

[en] Optical isotope shifts have been measured in eight spectral lines of samarium. The technique, which used tunable dye lasers and optical heterodyne methods, yielded uncertainties of +- 200 kHz. King plots involving two of the spectral lines with any of the other six show significant deviations from straight lines. The two anomalous transitions have the same upper level and show deviations of the isotope pair ¹⁵⁴Sm-¹⁵²Sm of 32 MHz from the expected values, other pairs deviating by only about 1 MHz. Effects due to fourth and higher moments of the nuclear-charge distribution do not appear able to explain these deviations within the framework of current theory. (author)

[en] GLOBAL acoustic oscillation modes of the Sun were discovered eleven years ago. The possibility of temporal variations in the oscillation frequencies was suggested by fluctuations in the flux of solar neutrinos, and would also be implied by changes in the solar cavity or in the speed of sound within the Sun. Our group has studied solar oscillations for many years; over the past decade, a network of three stations deployed at sites that can permit 24-h data collection has provided p-mode (acoustic) spectra of very high quality. Here we present evidence that the frequencies of the lowest-order (l ≤ 2) modes have varied over the period of observation (1977-88) in a manner that is correlated with solar activity (as measured by sunspot number). The frequency variation has a peak-to-peak amplitude of 0.46 ± 0.06 μHz, and could reflect variations in the solar dimensions or in the sound speed in the Sun, which might in turn be due to changes in solar temperature and/or magnetic field. (author)

[en] Differential extinction across the Earth's atmosphere affects astronomical photometry in a well known way. Under the same circumstances when a rotating extended object is observed spectrometrically, a residual radial velocity is obtained which varies during the day. In the case of integral sunlight observations, this effect has been calculated along the day in all possible observing situations during the year. Applications to real observations are shown and discussed leading to some conclusions specially relevant to ground-based networks

[en] Global oscillations of the Sun have been used to test solar models, but modelling the oscillation frequencies to their measured accuracies of a few microhertz has proved difficult, mostly owing to ignorance of the structure of the Sun's outer layers. The frequency separation between closely spaced modes in the acoustic spectrum is expected to depend more on core properties, however, and thus to provide constraints on models of the solar core. Our observations combine data from a global network of observing stations, which reduces the masking effect of daily sidebands in the spectral analysis. Here we present precision measurements of fine structure and its variation with frequency. Our results agree with standard solar models, and seem to remove the need for significant mixing or weakly interacting massive particles (WIMPS) in the core, both of which have been advanced to explain the low measured flux of solar neutrinos. This suggests that the solar neutrino problem must be resolved within neutrino physics, not solar physics; neutrino oscillations and a finite neutrino mass form a possible explanation. (author)

[en] Estimates of the spectral linewidths of low degree (l=0 and l=1), ''5 minute'' p-modes obtained from Doppler shift observations in 1984, 1986 and 1987 are reported. The observed linewidths increase from 0.5 μHz at 2000 μHz to 3.8 μHz at 4300 μHz for l = 0. Comparison with other data suggest that for a given frequency the linewidth increases with increasing l value. On the assumption that the linewidth is substantially due to damping processes the line widths are consistent with e-folding times between 3.7 and 0.5 days

[en] Analysis of data obtained over the years 1980-1985 are analyzed to show that the period of the 160-minute signal is indeed 160.00 minutes. It is demonstrated that this signal may be simulated by a slightly distorted diurnal sine wave such as that occasioned by differential atmospheric extinction. 15 refs