We describe a compact laser wavelength measuring instrument based on a small diffraction grating and a consumer-grade webcam. With just 1 pW of optical power, the instrument achieves absolute accuracy of 0.7 pm, sufficient to resolve individual hyperfine transitions of the rubidium absorption spectrum. Unlike interferometric wavemeters, the instrument clearly reveals multimode laser operation, making it particularly suitable for use with external cavity diode lasers and atom cooling and trapping experiments.

We describe an undergraduate laboratory that combines an accurate measurement of the speed of light, a fundamental investigation of a basic laser system, and a nontrivial use of statistical analysis. Students grapple with the existence of longitudinal modes in a laser cavity as they change the cavity length of an adjustable-cavity HeNe laser and tune the cavity to produce lasing in the TEM00 mode. For appropriate laser cavity lengths, the laser gain curve of a HeNe laser allows the simultaneous operation of multiple longitudinal modes. The difference frequency between the modes is measured using a self-heterodyne detection with a diode photodetector and a radio frequency spectrum analyzer. Asymmetric effects due to frequency pushing and frequency pulling, as well as transverse modes, are minimized by simultaneously monitoring and adjusting the mode structure as viewed with a Fabry–Pérot interferometer. The frequency spacing of longitudinal modes is proportional to the inverse of the cavity length with a proportionality constant equal to half the speed of light. By changing the length of the cavity, without changing the path length within the HeNe gas, the speed of light in air can be measured to be (2.9972±0.0002)×108 m/s, which is to high enough precision to distinguish between the speed of light in air and in vacuum.

The rubidium three-level ladder system consisting of the 5S, 5P and 5D states provides a readily accessible and powerful tool for extreme non-linear optics. We consider some phenomena and applications based on this system, including efficient frequency upconversion, state-selective cold atom imaging, and quantum squeezing.

The adsorption of tetravalent thorium on the muscovite mica (0 0 1) basal plane was studied by X-ray crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements and alpha spectrometry in the presence of perchlorate background electrolytes LiClO4, NaClO4, and KClO4 ([Th(IV)] = 0.1 mM, I = 0.1 M or 0.01 M, pH = 3.3 ± 0.3). RAXR data directly reveal a strong influence of the background electrolyte on the actinide sorption. No significant Th adsorption was observed in 0.1 M NaClO4, i.e., the Th coverage θ(Th), the number of Th per unit cell area of the muscovite surface (AUC = 46.72 Å2), was ⩽0.01 Th/AUC, whereas limited uptake (θ(Th) ∼ 0.04 Th/AUC) was detected at a lower ionic strength (I = 0.01 M). These results are in stark contrast to the behavior of Th in 0.1 M NaCl which showed a coverage of 0.4 Th/AUC (Schmidt et al., 2012a). Th uptake was also influenced by the electrolyte cation. Weak adsorption was observed in 0.1 M KClO4 (θ(Th) ∼ 0.07 Th/AUC) similar to the results in NaClO4 at lower ionic strength. In contrast, strong adsorption was found in 0.1 M LiClO4, with θ(Th) = 4.9 Th/AUC, a ∼10-fold increase compared with that previously reported in NaCl. These differences are confirmed independently by ex situ alpha spectrometry, which shows no measurable Th coverage in 0.1 M NaClO4 background in contrast to a large coverage of 1.6 Th/AUC in 0.1 M LiClO4. Alpha spectrometry cannot be obtained in situ, but sample preparation requires several washing steps that may affect Th(IV) sorption, RAXR, however, is considered to reflect the in situ sorption structure. The CTR/RAXR analyses of Th-LiClO4 show the sorption structure consisting of Th species that are broadly distributed, centered at heights of 4.1 Å and 29 Å distance from the interface. Neither the very large distribution height of the second species nor the high coverage can be explained with (hydrated) ionic adsorption, suggesting that the enhanced uptake is presumably due to the formation and sorption of Th nanoparticles.

We demonstrate production of continuous coherent blue laser light by using a five-level system in rubidium vapor. Two low-power lasers, at 780 and 776 nm, induce strong atomic coherence in the 5S-5P-5D states. The atoms decay to the 6P excited state, from which stimulated emission produces a coherent blue (420 nm) beam. We have coupled both ground-state hyperfine levels, effecting coherence between four levels. The coherent blue output is enhanced by several mechanisms, including stronger coupling to a larger fraction of the atomic population, operation at a detuning such that the vapor is nominally transparent to the 780 nm pump field, reduced losses owing to optical pumping, and optimal phase matching. We report experimental findings and compare them with results from a semiclassical Maxwell-Bloch model.

We demonstrate continuous coherent blue laser light production using a five-level lasing-without-inversion scheme in rubidium vapor. Two low-power lasers at 780 nm and 776 nm induce a strong atomic coherence in the 5S-5P-5D states. The atoms decay to the 6P excited state from which stimulated emission produces a coherent blue (420 nm) beam. We have coupled both ground-state hyperfine levels, effecting a coherent state between four levels. The coherent blue output is enhanced through several mechanisms, including stronger coupling to a larger fraction of the atomic population, operation at a detuning such that the vapor is nominally transparent to the 780 nm pump field, reduced losses due to optical pumping, and optimal phase-matching. We report experimental findings and compare with results from a semiclassical Maxwell-Bloch model. c © 2005 Optical Society of America

Since the early 1980s surveys of IT executives consistently ranked the development and operation of strategic information systems as a key management issue. Considerable prior research has been devoted to software development and pre-implementation phases of the system development life cycle, but only a few studies have investigated issues arising during the operational life of the system. These studies have reported conflicting results, and, consequently, offer little guidance to researchers and practitioners seeking to reduce the occurrence of operational failures in strategic information systems. The goal of this research was to identify the key elements responsible for accidents during the operation of strategic information systems and identify the relationships, if any, among these elements. In-depth interviews were conducted with 25 chief information officers using the critical incident technique to gather information about 41 specific strategic information operating failures, and these results were integrated with over 1,400 accident reports for a three year period from a major financial institution. The data was analyzed using Grounded Theory methodology and the key elements responsible for strategic information system accidents were identified as four key variables: Qualified management support of the operations environment characterized by lack of funding, lack of support for operations initiatives outside of the IT department, and perceived lack of IT credibility; Weak IT leadership characterized by passivity; Weak IT staff evidenced by lack of troubleshooting ability; and, Lack of operations information, which results in confusion and delays during accident recovery. Other contributions of the research include applying safety system concepts to business information systems, and creating and validating an accident classification framework.

Worldwide demand for qualified IT workers has employers exploring under-represented segments of the workforce. The percentage of women IT workers is not keeping pace with the growth of the industry. Minority populations, which are country specific, are also under-represented segments. This paper focuses on three significant minority segments in the United States: women, African Americans and Hispanic Americans. Studies have shown that increasing the number of these three groups enrolled in university computer science programs can help ease the shortage of qualified IT workers. One approach to attract and retain these students is to encourage the use of participatory organizations. This paper traces the initial efforts of one university to retain these segments through student-led chapters of the Association for Computing Machinery - Women, National Society of Black Engineers and Society of Hispanic Professional Engineers. Critical success factors are identified for use by other universities interested in initiating similar programs.

Reviewed by: After the Propaganda State: Media, Politics, and "Thought Work" in Reformed China James D. White (bio) Daniel C. Lynch . After the Propaganda State: Media, Politics, and "Thought Work" in Reformed China. Stanford: Stanford University Press, 1999. viii, 327 pp. Hardcover $45.00, ISBN 0-8047-3461-5. After the Propaganda State is a comprehensive overview of the media situation in China in the 1990s, and as such is most welcome. Any recent visitor to China is likely to be struck by the variety of media now available, in particular the number of television channels, but attempts to describe the situation in depth and to assess the ongoing impact of such diversity are all too few. Daniel C. Lynch's major findings are straightforward. He uses the inelegant reference term "thought work" (sixiang gongzuo)—defined as "the struggle to control communication flows and thus 'structuration' of the symbolic environment"— to describe how the Chinese state has to a large degree lost control of the public communication process. Not only can the Chinese leadership no longer rely on thought work to manage a fast-changing society, but the new media environment is in fact an accelerator of that loss of control. This does not translate into a direct political challenge, however. Although the mass media can play a key role in the development of public opinion and of alternative social networks, at present the government retains ultimate control of media outlets in China, which are driven by the market, and thus they should not be seen as components of a new, democratically oriented civil society in the making. Lynch begins by offering a short summary history of propaganda in China, which may be overly brief, as there is little sense of how the authoritarian tradition in China has always resulted in attempts at thought control. What does emerge clearly is how administrative fragmentation, property-rights reform, and technological advance have reduced the Chinese central party-state's ability to control thought work. These are essential points. In particular, property rights reform (more specifically, economic property rights) has produced a society where media entities—and their employees—are directly responsible for their own economic survival at the same time that their regulators benefit from their economic success. [End Page 507] Inevitably, "reform creates incentives for the regulators to 'turn a blind eye' to content that, although inconsistent with the party-state's thought work goals, appeals to larger audiences. The reason is simply that content with high audience appeal can serve as a magnet to attract advertisers, and advertising is now the major source of income for most media units" (p. 43). Lynch is especially effective in describing the elaborate dance between the management and employees of media work units and the officials charged with overseeing them, and how this plays out differently in different locations. The fires of economic imperatives—and the interregional competition fueled by administrative fragmentation—have also been fanned by the new technologies that have blown into China. Here the Chinese administration is caught between an ideological rock and a globalization hard place. "Unless China modernizes technologically, it will be unable to compete economically or militarily with the outside world. . . . China must integrate into the global economy in order to strengthen itself for competition. . . . A sharp reduction in control over thought work is simply the unavoidable price to be paid" (p. 45 ). Lynch gives numerous examples of how the logic of thought work continues to break down. He points out that the media have always been categorized as shiye, enterprises producing goods and services for the public good, in the same category as libraries, museums, and educational institutions—distinguishing them from qiye, enterprises operated as businesses, providing goods and services for gain. The rationale was that the primary function of the media was to promote the current propaganda line while also providing public-service information such as news and weather reports. This categorization allows the media to receive subsidies and to pay lower taxes. Times have changed, and in most cases the government can no longer afford to finance the media. But any attempt to rectify the situation has its dangers: if the de facto independent financial...

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Asymmetric dihydroxylation of (E)-ethyl 2-isopropylbut-2-enoate with AD-mix-alpha and AD-mix-beta, followed by saponification, gives (-)- and (+)-trachelanthic acids, respectively, which are each coupled via their acetonides with (+)-retronecine to yield the pyrrolizidine alkaloids indicine and intermedine.

The coadsorption of alkali atoms with Xe on a graphite substrate has been studied using He-atom scattering and low-energy electron diffraction (LEED). When Xe is adsorbed on a graphite surface which has a low density of alkali metal adatoms, ordered Xe monolayers and bilayers are formed. Differences in adsorption rate and desorption temperatures of the Xe indicate that the presence of alkali metal atoms on the surface increase the sticking coefficient and the desorption temperatures of Xe adatoms. As deduced from specular He-atom scattering desorption curves, this stronger adsorption behavior appears to be a local effect, causing the largest changes for Xe atoms next to the alkali metal adatoms. An increase in the Xe–graphite stretching frequency is also observed with inelastic He-atom scattering, consistent with the stronger adsorption of Xe. We observed no evidence for Xe adsorption onto full alkali metal overlayers down to 40 K, consistent with theoretical studies which indicate small physisorption well depths for rare gases on alkali metal surfaces.

He-scattering studies show that when alkali metal overlayers are present on a graphite surface the He-surface interaction has an extremely small corrugation, so small that no He diffraction was observed. He atoms do, however, couple to the overlayer phonons, and essentially dispersionless, low-energy modes were observed for K, Rb and Cs overlayers at submonolayer and monolayer coverages. Density-functional calculations for K and Cs on graphite indicate that the small surface corrugation experienced by the He atoms is due primarily to the large spatial extent of the alkali metal valence electrons, causing the turning point of the He atom to be significantly farther from the surface than for other materials. Also, at near-monolayer densities, the metallization of the overlayer produces an extremely smooth charge density. The vibrational modes observed with He-atom scattering are identified as modes polarized parallel to the surface. Modes which would correspond to a polarization perpendicular to the surface surprisingly are not observed. Growth of two and three layers were observed for Rb and Cs, respectively, their phonon energies decreasing and the amount of dispersion increasing for successive layers.

Low-energy (2.3–4.4 meV) vibrational modes have been observed from K, Rb, and Cs chemisorbed on the basal plane of graphite using inelastic He-atom scattering. These modes are interpreted as phonons propagating in the sagittal plane and polarized parallel to the surface plane. Modes having perpendicular polarization were undetectable. This anomalous result may be due to the coupling of the He atoms to the conduction electrons in the surface.

Theoretical calculations and experimental data are reported for He scattering from a graphite surface covered with an alkali-metal overlayer. The computed interaction potential has a very shallow well depth (⩽, 1 meV) in the case of a (2 × 2) layer. The predicted corrugation is also very small, corresponding to rather weak elastic diffraction beams. The calculated diffraction intensity is less than 2 percent of the specular intensity for a 17.4 meV He beam. No He diffraction was observed in the experiment on K, Rb, and Cs overlayers, indicating that these surfaces are even less corrugated than the calculation predicts.

In this paper, a new photoacoustic technique is described for measuring very low optical absorption in crystals and glasses. The technique differs from the conventional photoacoustic technique in that it does not use a high-power laser pulse to excite an acoustic signal in the sample, but instead uses a continuous laser with the beam modulated at an acoustic resonance frequency of the sample. By exciting the sample at resonance, the acoustic signal is enhanced by a factor proportional to the quality factor (Q) of the resonance. Because highly transparent crystals and glasses may have a Q on the order of 104 to 106, the technique is orders of magnitude more sensitive than conventional techniques. The Q is enhanced through the use of noncontact acoustic transducers, which also eliminate the problem of background signals due to scattered light. Measurements with various quartz samples have been used to verify the technique. Using a 10-W continuous laser, the noise level of the resonant photoacoustic technique would be equivalent to an optical absorption coefficient of ∼3×10−9 cm−1.