Short-wavelength free-electron laser sources and science: a review.

This review is focused on free-electron lasers (FELs) in the hard to soft x-ray regime. The aim is to provide newcomers to the area with insights into: the basic physics of FELs, the qualities of the radiation they produce, the challenges of transmitting that radiation to end users and the diversity of current scientific applications. Initial consideration is given to FEL theory in order to provide the foundation for discussion of FEL output properties and the technical challenges of short-wavelength FELs. This is followed by an overview of existing x-ray FEL facilities, future facilities and FEL frontiers. To provide a context for information in the above sections, a detailed comparison of the photon pulse characteristics of FEL sources with those of other sources of high brightness x-rays is made. A brief summary of FEL beamline design and photon diagnostics then precedes an overview of FEL scientific applications. Recent highlights are covered in sections on structural biology, atomic and molecular physics, photochemistry, non-linear spectroscopy, shock physics, solid density plasmas. A short industrial perspective is also included to emphasise potential in this area.

Excited electronic states of thiophene: high resolution photoabsorption Fourier transform spectroscopy and ab initio calculations.

The recently introduced synchrotron radiation-based Fourier transform spectroscopy has been employed to study the excited electronic states of thiophene. A highly resolved photoabsorption spectrum has been measured between ∼5 and 12.5 eV, providing a wealth of new data. High-level ab initio computations have been performed using the second-order algebraic-diagrammatic construction (ADC(2)) polarization propagator approach, and the equation-of-motion coupled-cluster (EOM-CC) method at the CCSD and CC3 levels, to guide the assignment of the spectrum. The adiabatic energy corrections have been evaluated, thereby extending the theoretical study beyond the vertical excitation picture and leading to a significantly improved understanding of the spectrum. The low-lying π→π* and π→σ* transitions result in prominent broad absorption bands. Two strong Rydberg series converging onto the X(~)(2)A2 state limit have been assigned to the 1a2→npb1(1)B2 and the 1a2→nda2(1)A1 transitions. A second, and much weaker, d-type series has been assigned to the 1a2→ndb1(1)B2 transitions. Excitation into some of the Rydberg states belonging to the two strong series gives rise to vibrational structure, most of which has been interpreted in terms of excitations of the totally symmetric ν4 and ν8 modes. One Rydberg series, assigned to the 3b1→nsa1(1)B1 transitions, has been identified converging onto the Ã(2)B1 state limit, and at higher energies Rydberg states converging onto the B(~)(2)A1 state limit could be identified. The present spectra reveal highly irregular vibrational structure in certain low energy absorption bands, and thus provide a new source of information for the rapidly developing studies of excited state non-adiabatic dynamics and photochemistry.

Submarine tower escape decompression sickness risk estimation.

Actions to enhance survival in a distressed submarine (DISSUB) scenario may be guided in part by knowledge of the likely risk of decompression sickness (DCS) should the crew attempt tower escape. A mathematical model for DCS risk estimation has been calibrated against DCS outcome data from 3,738 exposures of either men or goats to raised pressure. Body mass was used to scale DCS risk. The calibration data included more than 1,000 actual or simulated submarine escape exposures and no exposures with substantial staged decompression. Cases of pulmonary barotrauma were removed from the calibration data. The calibrated model was used to estimate the likelihood of DCS occurrence following submarine escape from the United Kingdom Royal Navy tower escape system. Where internal DISSUB pressure remains at - 0.1 MPa, escape from DISSUB depths < 200 meters is estimated to have DCS risk < 6%. Saturation at raised DISSUB pressure markedly increases risk, with > 60% DCS risk predicted for a 200-meter escape from saturation at 0.21 MPa. Using the calibrated model to predict DCS for direct ascent from saturation gives similar risk estimates to other published models.

Effect of oxygen adsorption on the chiral Pt{531} surface.

The adsorption of oxygen on the chiral Pt{531} surface was studied by high-resolution X-ray photoelectron spectroscopy (HRXPS) and low energy electron diffraction (LEED). After the surface is annealed in oxygen (3 x 10(-7) mbar), three O 1s peaks are observed in XPS. One peak, at 529.5 eV, is assigned to chemisorbed oxygen; it disappears after annealing in vacuo to temperatures above 900 K. The other two peaks at 530.8 and 532.3 eV are stable up to at least 1250 K. They are associated with oxide clusters on the surface. These clusters readily react with coadsorbed carbon monoxide at temperatures between 315 and 620 K.

Quantifying relativistic interactions from angular momentum partitioning measurements during photoionization.

We have measured the degree of helicity of fluorescent radiation from Ar+[3p4[3P]4p] 2P(o)1/2 formed by circularly polarized synchrotron radiation in the region of double excitations converging to Ar+3p4 nl satellite states. Angular momentum coupling allows the partitioning of the one unit of angular momentum brought into the system to be demarcated. We obtain a nonvanishing expectation value of the total spin of the residual ion-photoelectron system indicating significant relativistic interactions during the photoionization process.

Long-term effects of a psychologically based group programme for women preoccupied with body weight and eating behaviour.

The effects of a 10 session group programme designed to discourage dieting behaviour and reduce preoccupation with body weight, food and eating were assessed in 87 women (mean age 40 years and mean body mass index 31.9) who attended three different agencies in Adelaide, South Australia. The subjects were selected on the basis of eating preoccupation and not body weight. Measurements of various psychological parameters and body weight were made at entry to the programme, at the completion of the programme and at 6 months, 1 year and 2 years after its completion. Eighty women completed the groups and data were obtained from 56 of them at 2 years. At the completion of the group programme and at 2 years there were significant improvements (P less than 0.01) in the psychological parameters self-esteem, depression, self-image, eating attitude, body image and assertion. At two years after the completion of the group, there was a significant (P less than 0.005) mean weight loss of 3.1 kg when compared to baseline. We conclude that this programme confers long-term beneficial effects on psychological function and body weight.

Detailed electronic description of triple bonds between transition metal atoms and verification by photoelectron spectroscopy.

Using the SCF-Xalpha-SW method the ground state electronic structures of (HO)(3)Mo identical withMo(OH)(3), (H(2)N)(3)Mo identical withMo(NH(2))(3), and (Me(2)N)(3)Mo identical withMo(NMe(2)) have been calculated. The results provide a detailed description of the metal-to-metal triple bonds present; some of the more important molecular orbitals are shown in detail as contour diagrams. The energy levels of all filled valence shell/molecular orbitals and the lower virtual orbitals are presented in diagrams. The pi(e(u)) and sigma(a(1g)) orbitals which have large amounts of metal character can be identified as the orbitals primarily responsible for Mo-Mo bonding. Using the transition state technique to allow for relaxation effects, the photoelectron spectra (up to 12 eV) have been calculated for Mo(2)(OH)(6) and Mo(2)(NH(2))(6) and found to compare very well, after applying a constant downshift to correct for inductive effects, with experimental spectra for Mo(2)[OCH(2)C(CH(3))(3)](6) and Mo(2)[N(CH(3))(2)](6). The experimental photoelectron spectra are reported.