ArI2(X)→Ar+I2(B) photodissociation: Comparison between linear and T-shaped isomers dynamics

An attempt was made to compute the spectra and product state distributions on semiempirical and ab initio electronic potential energy surfaces for both linear and T-shaped ArI2(X) isomers. It was shown that whereas the T-shaped isomer dynamics is dominated by resonances, dissociation of the linear isomer involves competition between a fast direct process and slower vibrational predissociation of near-linear resonances.This work has been supported by DGICYT @Ministerio de Educación y Ciencia (MEC), Spain, under Grant No. PB95- 0071, INTAS under Grant No. 97-31573 and the SpanishFrench PICASSO project No. HF1999-0132. One of authors (A.A.B) also thanks MEC for sabbatical fellowship.Peer Reviewe

A wave packet Golden Rule treatment of vibrational predissociation

The time-dependent wave packet technique is applied to the Golden Rule treatment of vibrational predissociation. The wave packet at time zero is taken as the product of the quasibound wave function and the coupling inducing predissociation. The rate for vibrational predissociation can then be obtained by Fourier transform into the energy domain of the time-dependent wave packet autocorrelation function. The method has been applied to a model triatomic van der Waals molecule. It is shown that when the bound-state components of the wave packet are projected out, the time-dependent version of the Golden Rule approximation provides an alternative efficient technique to treat intramolecular decay. © 1991 American Institute of Physics.Peer Reviewe

Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen

While measurements of the hyperfine structure of hydrogen-like atoms are traditionally regarded as test of bound-state QED, we assume that theoretical QED predictions are accurate and discuss the information about the electromagnetic structure of protons that could be extracted from the experimental values of the ground state hyperfine splitting in hydrogen and muonic hydrogen. Using recent theoretical results on the proton polarizability effects and the experimental hydrogen hyperfine splitting we obtain for the Zemach radius of the proton the value 1.040(16) fm. We compare it to the various theoretical estimates the uncertainty of which is shown to be larger that 0.016 fm. This point of view gives quite convincing arguments in support of projects to measure the hyperfine splitting of muonic hydrogen.Comment: Submitted to Phys. Rev.

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

A three-dimensional wave packet study of Ar⋯I2(B)→Ar + I + I electronic predissociation

A three-dimensional wave packet study of Ar⋯I2(B)→ Ar + I(2P3/2)+ I(2P3/2) electronic predissociation, arising from the argon-induced electrostatic coupling between the B(3Π0+u) and the repulsive a(3Π1g) state of I2, is presented. A time-dependent golden rule approach is used. The initial wave packet corresponds to a bound vibrational wave function of the Ar⋯I2(B) complex (with zero total angular momentum) multiplied by the electronic coupling. A 3-D propagation in the final dissociative surface is then performed and the predissociation rates are obtained by Fourier transform of the wave packet autocorrelation function. The potential energy surfaces are described by sums of atom-atom interactions. For the B(3Π0+u) state potential, empirically determined van der Waals parameters available from the literature are used. For the final dissociative a(3Π1g) electronic state, the van der Waals parameters are adjusted to reproduce the experimentally observed oscillations of the electronic predissociation rate as a function of the initial vibrational quantum number υ′ of I2. It is shown that good agreement between calculated and measured values can be obtained with a van der Waals well of 100 cm-1 and an interstate coupling of the order of 14 cm-1. © 1996 American Institute of Physics.We acknowledge support from the CNRS for the use of the computing facilities at IDRIS, and the European Community for visiting support ~SCT-CT91-0699!. One of us (O.R.) was supported by a grant from DGICYT No. PB92- 0053 and Comunidad Autónoma de Madrid No. 064/92.Peer Reviewe

On the orientation of molecular photofragments produced in highly excited rotational states

The degree of orientation of highly excited rotational states of molecular fragments produced by photodissociation with circularly polarized light is studied quantum mechanically. It is shown that a significant orientation of the fragments' angular momentum j can be obtained when two or more dissociative continua correlated to the same final state of the products are excited simultaneously. In addition, the coherently excited continua should correspond to different helicity states, that is, to different projections of j on the reaction coordinate R (the vector joining the centers of mass of the fragments). The particular cases of an initial total angular momentum equal to zero as well as the axial recoil limit are discussed. The theory is applied to a simplified model of the photodissociation of ICN in the A continuum. The calculations have been performed by integration of the time independent quantum close-coupling equations for the coupling between the rotation of CN and the reaction coordinate R, using recently proposed potential energy surfaces and couplings. The results reproduce qualitatively the experimental results of Hasselbrink, Waldeck, and Zare [Chem. Phys. 126, 191 ( 1988)], in particular, the change of sign and the large degree of orientation found for highly excited rotational states of the CN fragments. © 1992 American Institute of Physics.The calculations presented here were carried out on the VP200 computer at CIRCE (Orsay).Peer Reviewe