Quasisimultons in Thermal Atomic Vapors.

The propagation of two-color laser fields through optically thick atomic ensembles is studied. We demonstrate how the interaction between these two fields spawns the formation of copropagating, two-color solitonlike pulses akin to the simultons found by Konopnicki and Eberly [Phys. Rev. A 24, 2567 (1981)PLRAAN0556-279110.1103/PhysRevA.24.2567]. For the particular case of thermal Rb atoms exposed to a combination of a weak cw laser field resonant on the D1 transition and a strong sub-ns laser pulse resonant on the D2 transition, simulton formation is initiated by an interplay between the 5s_{1/2}-5p_{1/2} and 5s_{1/2}-5p_{3/2} coherences. The interplay amplifies the D1 field at the arrival of the D2 pulse, producing a sech-squared pulse with a length of less than 10 µm. This amplification is demonstrated in a time-resolved measurement of the light transmitted through a thin thermal cell. We find good agreement between experiment and a model that includes the hyperfine structure of the relevant levels. With the addition of Rydberg dressing, quasisimultons may offer interesting prospects for strong photon-photon interactions in a robust environment.

Optical response of gas-phase atoms at less than λ/80 from a dielectric surface.

We present experimental observations of atom-light interactions within tens of nanometers (down to 11 nm) of a sapphire surface. Using photon counting we detect the fluorescence from of order one thousand Rb or Cs atoms, confined in a vapor with thickness much less than the optical excitation wavelength. The asymmetry in the spectral line shape provides a direct readout of the atom-surface potential. A numerical fit indicates a power law -C(α)/r(α) with α = 3.02 ± 0.06 confirming that the van der Waals interaction dominates over other effects. The extreme sensitivity of our photon-counting technique may allow the search for atom-surface bound states.

A survey of community placements for educational programmes in nursing and midwifery.

In this paper preliminary findings from the first stage of an English National Board (ENB) commissioned study investigating the educational needs of community practitioners in relation to their responsibilities for student learning are presented. A national postal survey of all educational centres offering nurse and/or midwifery education was undertaken in the latter half of 1993. Information was collected regarding the nature and planning of the community practice components of courses. The main methods of support for practitioners included the provision of the ENB 998/997 courses and liaison meetings between educational centres and community practice areas. Practitioners were often required to both supervise and assess students on practice placements, the length of these placements varying enormously. For those centres offering the mental health and learning disability branches of the Diploma in Higher Education in Nursing Studies (Project 2000), a significant proportion lacked teachers with specialist community qualifications. The investigation took place at a time of great upheaval, with 42% of centres reporting that they were in the process of amalgamation. The findings demonstrate that community nurses and midwives undoubtedly contribute to the education of nurse and midwife students and consequently have educational needs which must be addressed if they are to continue to supervise students.