Laser-induced rotation of iodine molecules in He-nanodroplets: revivals and breaking-free

Rotation of molecules embedded in He nanodroplets is explored by a combination of fs laser-induced alignment experiments and angulon quasiparticle theory. We demonstrate that at low fluence of the fs alignment pulse, the molecule and its solvation shell can be set into coherent collective rotation lasting long enough to form revivals. With increasing fluence, however, the revivals disappear -- instead, rotational dynamics as rapid as for an isolated molecule is observed during the first few picoseconds. Classical calculations trace this phenomenon to transient decoupling of the molecule from its He shell. Our results open novel opportunities for studying non-equilibrium solute-solvent dynamics and quantum thermalization.Comment: 6+7 pages; 4+1 figures; 1 tabl

Strongly aligned molecules inside helium droplets in the near-adiabatic regime

Iodine (I$_2$) molecules embedded in He nanodroplets are aligned by a 160 ps long laser pulse. The highest degree of alignment, occurring at the peak of the pulse and quantified by $\langle \cos^2 \theta_{2D} \rangle$, is measured as a function of the laser intensity. The results are well described by $\langle \cos^2 \theta_{2D} \rangle$ calculated for a gas of isolated molecules each with an effective rotational constant of 0.6 times the gas-phase value, and at a temperature of 0.4 K. Theoretical analysis using the angulon quasiparticle to describe rotating molecules in superfluid helium rationalizes why the alignment mechanism is similar to that of isolated molecules with an effective rotational constant. A major advantage of molecules in He droplets is that their 0.4 K temperature leads to stronger alignment than what can generally be achieved for gas phase molecules -- here demonstrated by a direct comparison of the droplet results to measurements on a $\sim$ 1 K supersonic beam of isolated molecules. This point is further illustrated for more complex system by measurements on 1,4-diiodobenzene and 1,4-dibromobenzene. For all three molecular species studied the highest values of $\langle \cos^2 \theta_{2D} \rangle$ achieved in He droplets exceed 0.96.Comment: 11 pages, 8 figure

Hyperfine-Structure-Induced Depolarization of Impulsively Aligned I2\rm I_2 Molecules

A moderately intense $450$ fs laser pulse is used to create rotational wave packets in gas phase $\rm{I_2}$ molecules. The ensuing time-dependent alignment, measured by Coulomb explosion imaging with a delayed probe pulse, exhibits the characteristic revival structures expected for rotational wave packets but also a complex non-periodic substructure and decreasing mean alignment not observed before. A quantum mechanical model attributes the phenomena to coupling between the rotational angular momenta and the nuclear spins through the electric quadrupole interaction. The calculated alignment trace agrees very well with the experimental results.Comment: 6 pages, 4 figures, and Supplementary Information. This article has been accepted for publication in Physical Review Letter

Gurga Chiya and Tepe Marani: new excavations in the Shahrizor plain, Iraqi Kurdistan

Gurga Chiya and Tepe Marani are small, adjacent mounds located close to the town of Halabja in the southern part of the Shahrizor Plain, one of the most fertile regions of Iraqi Kurdistan. Survey and excavation at these previously unexplored sites is beginning to produce evidence for human settlement spanning the sixth to the fourth millennia, c. 5600–3300 cal. b.c. In Mesopotamian chronology this corresponds to the Late Neolithic through to Chalcolithic periods; the Halaf, Ubaid, and Uruk phases of conventional culture history. In Iraqi Kurdistan, documentation of these periods—which witnessed many important transformations in prehistoric village life—is currently very thin. Here we offer a preliminary report on the emerging results from the Shahrizor Plain, with a particular focus on the description of material culture (ceramic and lithic assemblages), in order to establish a benchmark for further research. We also provide a detailed report on botanical remains and accompanying radiocarbon dates, which allow us to place this new evidence in a wider comparative framework. A further, brief account is given of Late Bronze Age material culture from the upper layers at Gurga Chiya. We conclude with observations on the significance of the Shahrizor Plain for wider research into the later prehistory of the Middle East, and the importance of preserving and investigating its archaeological record

Rotational coherence spectroscopy of molecules in helium nanodroplets: Reconciling the time and the frequency domains

Alignment of OCS, CS$_2$ and I$_2$ molecules embedded in helium nanodroplets is measured as a function of time following rotational excitation by a non-resonant, comparatively weak ps laser pulse. The distinct peaks in the power spectra, obtained by Fourier analysis, are used to determine the rotational, B, and centrifugal distortion, D, constants. For OCS, B and D match the values known from IR spectroscopy. For CS$_2$ and I$_2$, they are the first experimental results reported. The alignment dynamics calculated from the gas-phase rotational Schr\"{o}dinger equation, using the experimental in-droplet B and D values, agree in detail with the measurement for all three molecules. The rotational spectroscopy technique for molecules in helium droplets introduced here should apply to a range of molecules and complexes.Comment: ASC and LC contributed equally. 7 pages, 3 figure

Culture, government, and spatiality: re-assessing the 'Foucault effect' in cultural-policy studies

This article critically discusses the reconceptualization of culture and governmentality in recent Australian ‘cultural–policy studies’. It argues that the further development of this conceptualization requires a more careful consideration of the complex relations between culture, power and the different spatialities of social practices. The assumptions of this literature regarding social-democratic public institutions and the nation-state are critically addressed in the light of contemporary processes of globalization. It is argued that the use made of Foucault in this paradigm privileges a model of disciplinary power which is dependent on a particular spatialization of social subjects and technologies of the self. As a result, an uncritical application of this model to all cultural practices supports a far too coherent image of practices of ‘government’ in producing sought-after subject-effects. It is suggested that the different articulations of spatio-temporal presence and absence in cultural technologies require a less totalizing understanding of the forms of power exercised through governmental practices

Transformative sensemaking: Development in Whose Image? Keyan Tomaselli and the semiotics of visual representation

The defining and distinguishing feature of homo sapiens is its ability to make sense of the world, i.e. to use its intellect to understand and change both itself and the world of which it is an integral part. It is against this backdrop that this essay reviews Tomaselli's 1996 text, Appropriating Images: The Semiotics of Visual Representation/ by summarizing his key perspectives, clarifying his major operational concepts and citing particular portions from his work in support of specific perspectives on sense-making. Subsequently, this essay employs his techniques of sense-making to interrogate the notion of "development". This exercise examines and confirms two interrelated hypotheses: first, a semiotic analysis of the privileged notion of "development" demonstrates its metaphysical/ ideological, and thus limiting, nature especially vis-a-vis the marginalized, excluded, and the collective other, the so-called Developing Countries. Second, the interrogative nature of semiotics allows for an alternative reading and application of human potential or skills in the quest of a more humane social and global order, highlighting thereby the transformative implications of a reflexive epistemology.Web of Scienc

Young children\u27s individuation of object sets: Grasping an alternative unit of count

Young children\u27s concept of what units can be counted—for example, individuals, classes and kinds—changes with age. It is important to understand how young children master the concept of counting varied units given that mastering alternative units is a basic skill in understanding our base system of counting (e.g., understanding that ten tens equal 100). An ability to enumerate classes would appear to be one precursor to being able to adopt alternative units of counting and to attaining later math concepts (i.e., base systems). The facilitation of 4-year-olds ability to enumerate classes was examined for three variables: (1) alternative class labels, (2) salient unifiers (containment) and (3) set size. In Experiments 1 and 2, four-year-olds\u27 ability to enumerate classes with different labels was examined. In Experiment 3, four-year-olds\u27 ability to enumerate classes with contained sets was examined. Lastly, in Experiment 4, four-year-olds\u27 ability to enumerate classes with large size sets was examined. Overall, about 50% the subjects could not quantify classes: most children\u27s responses were bimodal. A bias to process discrete physical entities rather than labels or perceptual properties appears to account for the children\u27s performance

The recycling of [existing] structures for low and moderate income subsidized housing

Thesis (M.Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1980.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.Includes bibliographical references.by Shepperson A. Wilbun, Jr.M.Arch