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Resonant two-photon threshold ionization spectroscopy is employed to determine the ionizationenergy of C2 to 5 meV precision, about two orders of magnitude more precise than the previously accepted value. Through exploration of the ionization threshold after pumping the 0-3 band of the newly discovered 4³Πg←a³Πu band system of C2, the ionizationenergy of the lowest rovibronic level of the a³Πu state was determined to be 11.791(5) eV. Accounting for spin-orbit and rotational effects, we calculate that the ionizationenergy of the forbidden origin of the a³Πu state is 11.790(5) eV, in excellent agreement with quantum thermochemical calculations which give 11.788(10) eV. The experimentally derived ionizationenergy of X¹Σg+X¹Σg+ state C2 is 11.866(5) eV. [ABSTRACT FROM AUTHOR]

The unimolecular photodissociation dynamics of acetone spanning the entire S 1 ← S 0 absorption spectrum have been reinvestigated, with a focus on mechanisms that produce CO. At excitation wavelengths of λ > 305.8 nm, all photoproducts are formed on the S 0 state after internal conversion. A roaming mechanism forming C 2 H 6 + CO is active in the window λ = 311.2-305.8 nm. From λ = 305.8 to 262 nm, little or no CO is produced with the photochemistry dominated by the Norrish-type I C-C bond cleavage on the lowest excited triplet state, T 1 . At higher energy (λ < 262 nm), an increasing fraction of CH 3 CO radicals from the primary reaction have sufficient internal energy to spontaneously decompose to CH 3 + CO. A new model is presented to account for the kinetic energy distribution of the secondary CH 3 radical, allowing us to determine the height of the energetic barrier to CH 3 CO decomposition as 68 ± 4 kJ mol -1 , which lies midway between previous measurements. The fraction of CO from triple fragmentation rises smoothly from 260 to 248 nm. We see no evidence of the return of roaming, or any other S 0 reaction, in this higher energy region of the first electronic absorption band.

The lowest 13 vibrational levels, v = 0-12, of the eΠg3 state of the C 2 molecule have been measured by laser-induced fluorescence of new bands of the Fox-Herzberg system. The newly observed levels, v = 5-12, which span the eΠg3 electronic state up to and beyond the first dissociation threshold of C 2 , were analyzed to afford highly accurate molecular constants, including band origins, and rotational and spin-orbit constants. The spin-orbit coupling constants of the previously published lowest five levels are revised in sign and magnitude, requiring an overhaul of previously published molecular constants. The analysis is supported by high level ab initio calculations. Lifetimes of all observed levels were recorded and found to be in excellent agreement with ab initio predicted values up to v = 11. v = 12 was found to exhibit a much reduced lifetime and fluorescence quantum yield, which is attributed to the onset of predissociation. This brackets the dissociation energy of ground state XΣg+1 C 2 between 6.1803 and 6.2553 eV, in agreement with the Active Thermochemical Tables.

The 3 3 Π g state of the dicarbon molecule, C 2 , has been identified for the first time by a combination of resonant ionization spectroscopy, mass spectrometry, and high-level ab initio quantum chemical calculations. This marks the discovery of the final valence triplet state of C 2 spectroscopically accessible from the lowest triplet state. It is found to be vibronically coupled to the recently discovered 4 3 Π g state, necessitating vibronic calculations beyond the Born-Oppenheimer approximation to reconcile calculated rotational constants with observations. The 3 3 Π g state of C 2 is observed to have a much shorter fluorescence lifetime than expected, possibly pointing to predissociation by coupling to the unbound d 3 Π g state.

A high-resolution single vibronic level emission study from the A (2)Pi(32) state of the HC(4)S radical is reported. Ground state density functional theory frequencies have been used to assign ground state vibronic levels involving three stretching modes nu(2), nu(3), and nu(5) in the region of 0-3250 cm(-1), while the frequency of nu(4) remains speculative. Tentative assignments are given for the complicated structures arising from Renner-Teller and spin-orbit interactions within the bending energy levels. From analysis of the dispersed emission spectra, Fermi resonances involving pairs of bands have been identified in the A (2)Pi(32)<--X (2)Pi(32) laser induced fluorescence spectrum.

Objectives: To determine whether a previously-validated touch screen computer program of symptoms and management of childhood asthma is acceptable to parents who accompany their children to consult a GP, and to examine whether any parent characteristics are associated with acceptability., Methods: Conducted in general practice in Newcastle, NSW, Australia. A cross sectional pen and paper survey was given to parents of children consulting a GP after completing the computer questionnaire on childhood asthma in the waiting room. Measurements were frequencies of Likert scale responses to statements concerning the computer questionnaire, compared with demographic and personal characteristics., Results: High levels of acceptability of the asthma computer questionnaire were reported by the 198 respondents, with most being willing to do the same program once or twice a year (87%), or to do similar programs on other topics (91%). Most respondents (81%) agreed that the computer program was enjoyable, and very few (8%) would have preferred to answer the asthma questions by pen and paper rather than by computer. Two or more children accompanying the parent was the characteristic most associated with less positive responses., Conclusions: Overall the high acceptability of this questionnaire suggests that this computerised format is an appropriate method of screening children for asthma and determining their current management. As a large component of underdiagnosis of asthma is lack of reporting to the doctor, this valid and acceptable diagnostic aid has the potential to improve detection of unreported asthma, and also to identify high-risk individuals.

Aim: To gauge the importance and relevance placed by general practitioners on components of the National Asthma Campaign's 'Six step' Asthma Management Plan for childhood asthma., Method: A cross sectional postal survey of a national randomised sample of 824 GPs., Results: Each component was considered to be 'quite' or 'very' important by at least 70% of respondents. All 11 components were rated to be either 'quite' or 'very' important by 44%, and 91% of respondents considered eight or more of the components to be 'quite' or 'very' important. Two characteristics were consistently associated with the rating of importance: gender, (women GPs generally showing higher ratings), and reported frequency of use of the Asthma Management Plan (frequent users rate importance more frequently)., Conclusion: There were high levels of endorsement of the Asthma Management Plan for children with asthma.

Background: Childhood asthma remains underdiagnosed in general practice. Computers with a patient interface have the potential to screen children for asthma in a time-efficient manner., Aim: To develop a concise, validated self-report measure that calculates an 'asthma score' that predicts likelihood of asthma and its severity in childhood., Design of Study: Computerised questionnaire survey in general practitioners' (GPs') waiting rooms, followed by a written questionnaire and either bronchial challenge or skin allergy testing at the regional teaching hospital., Setting: Children between 18 months and 18 years old accompanied by a parent or guardian in five group practices in Newcastle in New South Wales, Australia., Method: The responses from both the computerised questionnaire and the written questionnaire were compared with physician assessment of asthma, based on an existing validated questionnaire and clinical tests., Results: Six items were identified to be independently and significantly associated (at P < 0.05) with the presence of asthma and its severity: parent or self-reported asthma, previous diagnosis, wheeze in the past year, physical activity affected by symptoms, night cough in the past year, and visits to a GP in the past year. From the regression model a linear score was derived that indicates whether a child is likely to have asthma and its likely severity., Conclusions: The asthma score is a valid indicator of asthma and its severity in children in general practice.