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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]

Background: Anorexia nervosa may cause several gastro-intestinal complications., Case Description: A 21-year-old woman presented herself with abdominal pain and vomiting a day after her first binge-eating episode. In her recent history she had lost 40 kg in weight and her BMI was 15 at presentation. Imaging showed gastric distension and ascites in all quadrants, suspicious of a gastric rupture. A blow-out of the stomach was seen during a diagnostic laparotomy, which was treated with a gastric sleeve procedure. Following surgery, the patient was diagnosed with anorexia nervosa of the restrictive type with a first episode of binge-eating., Conclusion: Gastric rupture is a rare and unknown complication of anorexia nervosa with a high mortality.

Formaldehyde, HCHO, is the highest-volume carbonyl in the atmosphere. It absorbs sunlight at wavelengths shorter than 330 nm and photolyses to form H and HCO radicals, which then react with O 2 to form HO 2 . Here we show HCHO has an additional HO 2 formation pathway. At photolysis energies below the energetic threshold for radical formation we directly detect HO 2 at low pressures by cavity ring-down spectroscopy and indirectly detect HO 2 at 1 bar by Fourier-transform infrared spectroscopy end-product analysis. Supported by electronic structure theory and master equation simulations, we attribute this HO 2 to photophysical oxidation (PPO): photoexcited HCHO relaxes non-radiatively to the ground electronic state where the far-from-equilibrium, vibrationally activated HCHO molecules react with thermal O 2 . PPO is likely to be a general mechanism in tropospheric chemistry and, unlike photolysis, PPO will increase with increasing O 2 pressure., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Excitation spectra of protonated and deuteronated anthracene are obtained by triple-resonance dissociation spectroscopy. Very cold cations, protonated/deuteronated exclusively at the 9-position, are generated from two-colour two-photon threshold ionisation of 9-dihydroanthracenyl radicals (C 14 H 11 ). The excitation spectra reveal rich structure, not resolved in previous studies, that is assigned based on anharmonic and Herzberg-Teller coupling calculations. This work reveals that the excitation of protonated anthracene induces a symmetry-breaking intramolecular charge-transfer process along a Marcus-Hush coordinate, where the positively charged hole hops from the central bridging sp 2 carbon, onto one of the aromatic rings. Signatures of this charge-transfer event are observed in the excitation spectrum, through active Herzberg-Teller progressions.

A new technique is reported to determine absolute photodissociation quantum yields, ϕ diss , in a molecular beam. The technique relies on a molecule having two available product channels, where a species in channel A can be converted photolytically to a species in channel B. The relative decrease in the species from channel A and the relative increase in species from B provide a direct measure of the relative product yield of each channel, with no external calibration required. In the event that only channels A and B exist, or at least dominate, then the sum rule ϕ A + ϕ B = 1 can be used to convert relative quantum yields into absolute yields. The technique is demonstrated using the well-understood and characterized photochemistry of HCHO. Formaldehyde photolysis at wavelengths near 310 nm produces either H + HCO (channel A) or H 2 + CO (channel B). HCO can then be photolyzed with high efficiency into H + CO. The product state distributions for HCO from channel A, CO from channel B, and CO from the secondary HCO photolysis event are all well-known; this is not a requirement but is utilized here to demonstrate the veracity of the technique. The zero-pressure quantum yields of HCO from HCHO photolysis via the 2 3 4 1 and 2 1 5 1 states of HCHO are determined to be 0.66 and 0.74, respectively, which are in excellent agreement with the established quantum yields at atmospheric pressure and support the conclusion that HCHO quantum yields at these photolysis energies are not pressure dependent.

Despite the long history of spectroscopic studies of the C 2 molecule, fundamental questions about its chemical bonding are still being hotly debated. The complex electronic structure of C 2 is a consequence of its dense manifold of near-degenerate, low-lying electronic states. A global multi-state diabatic model is proposed here to disentangle the numerous configuration interactions that occur within four symmetry manifolds of excited states of C 2 ( 1 Π g , 3 Π g , 1 Σ u + , and 3 Σ u + ). The key concept of our model is the existence of two "valence-hole" configurations, 2 σ g 2 2 σ u 1 1 π u 3 3 σ g 2 for 1,3 Π g states and 2 σ g 2 2 σ u 1 1 π u 4 3 σ g 1 for 1,3 Σ u + states, that are derived from 3σ g ← 2σ u electron promotion. The lowest-energy state from each of the four C 2 symmetry species is dominated by this type of valence-hole configuration at its equilibrium internuclear separation. As a result of their large binding energy (nominal bond order of 3) and correlation with the 2s 2 2p 2 + 2s2p 3 separated-atom configurations, the presence of these valence-hole configurations has a profound impact on the global electronic structure and unimolecular dynamics of C 2 .

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.

Polycyclic aromatic hydrocarbons (PAHs) are intermediates in the formation of soot particles and interstellar grains. However, their formation mechanisms in combustion and interstellar environments are not fully understood. The production of tricyclic PAHs and, in particular, the conversion of a PAH containing a five-membered ring to one with a six-membered ring are of interest to explain PAH abundances in combustion processes. In the present work, resonant ionization mass spectrometry in conjunction with isotopic labeling is used to investigate the formation of the phenalenyl radical from acenaphthylene and methane in an electrical discharge. We show that in this environment the CH cycloaddition mechanism converts a five-membered ring to a six-membered ring. This mechanism can occur in tandem with other PAH formation mechanisms such as hydrogen abstraction/acetylene addition (HACA) to produce larger PAHs in flames and the interstellar medium.

The dicarbon molecule (C 2 ) is found in flames, comets, stars, and the diffuse interstellar medium. In comets, it is responsible for the green color of the coma, but it is not found in the tail. It has long been held to photodissociate in sunlight with a lifetime precluding observation in the tail, but the mechanism was not known. Here we directly observe photodissociation of C 2 From the speed of the recoiling carbon atoms, a bond dissociation energy of 602.804(29) kJ·mol[Formula: see text] is determined, with an uncertainty comparable to its more experimentally accessible N 2 and O 2 counterparts. The value is within 0.03 kJ·mol -1 of high-level quantum theory. This work shows that, to break the quadruple bond of C 2 using sunlight, the molecule must absorb two photons and undergo two "forbidden" transitions., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

The photodissociation dynamics of jet-cooled trifluoroacetaldehyde (CF 3 CHO) into radical products, CF 3 + HCO, was explored using velocity mapped ion imaging over the wavelength range 297.5 nm ≤λ≤ 342.8 nm (33 613-29 172 cm -1 ) covering the entire section of the absorption spectrum accessible with solar actinic wavelengths at the ground level. After initial excitation to the first excited singlet state, S 1 , the radical dissociation proceeds largely via the first excited triplet state, T 1 , at excitation energies above the T 1 barrier. By combining velocity-mapped ion imaging with high-level theory, we place this barrier at 368.3 ± 2.4 kJ mol -1 (30 780 ± 200 cm -1 ). After exciting to S 1 at energies below this barrier, the dissociation proceeds exclusively via the ground electronic state, S 0 . The dissociation threshold is determined to be 335.7 ± 1.8 kJ mol -1 (28 060 ± 150 cm -1 ). Using laser-induced fluorescence spectroscopy, the origin of the S 1 ← S 0 transition is assigned at 28 903 cm -1 . The S 0 dissociation channel is active at the S 1 origin, but the yield significantly increases above 29 100 cm -1 due to enhanced intersystem crossing or internal conversion.

Objective: Psychiatric comorbidities are common in physical illness and significantly affect health outcomes. Attitudes of general hospital doctors toward psychiatry are important as they influence referral patterns and quality of care. Little is known about these attitudes and their cultural correlates. The aim of this study was to identify attitudes toward psychiatry among general hospital specialists in relation to culture of the practice setting and other clinician factors (gender, age, seniority and specialty)., Methods: A cross-sectional, descriptive study was carried out in seven countries (New Zealand, China, Sri Lanka, Russia, Israel, Brazil, the Netherlands). Data were collected from senior medical staff of various disciplines using an updated version of Mayou and Smith's (1986) self-administered questionnaire., Results: A total of 889 hospital doctors participated. While favourable attitudes toward both psychiatric consultation and management were endorsed by a majority, significant differences were also observed between countries. Subgroup differences were mostly confined to gender, acuity of practice setting and specialty. For example, female doctors in Russia (χ 2 =7.7, p=0.0056), China (χ 2 =9.2, p=0.0025) and the Netherlands (χ 2 =5.7, p=0.0174) endorsed more positive attitudes compared with their male counterparts, but this gender effect was not replicated in the total sample. Chronic care specialists were overall more inclined to manage patients' emotional problems compared with those working in acute care (χ 2 =70.8, p (adjusted)<0.0001), a significant finding seen also in individual countries (China, New Zealand, the Netherlands, Russia). Physicians were more favourably disposed toward psychiatry compared with other specialists, especially surgeons, in all countries except Israel., Conclusions: This study adds to evidence for the association of medical attitudes with individual clinician factors and demonstrates that the influence of these factors varies by country. Understanding these issues may help to overcome barriers and improve quality of care provided to general hospital patients., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Since its discovery 16 years ago, roaming has become a ubiquitous mechanism in molecular photochemistry. Its general features are now understood, but little detail is known about how the potential energy surface (PES) determines reaction outcomes. We performed detailed experiments on formaldehyde (H 2 CO) photodissociation and determined fully correlated quantum state distributions of the molecular hydrogen and carbon monoxide products. These experiments reveal previously undetected bimodal carbon monoxide rotational distributions. Insights from classical trajectory calculations demonstrate that these features arise from resonances as the PES directs the reaction into cis and trans O-C-H···H critical geometries, which produce rebound and stripping mechanisms, respectively. These subtle and pervasive effects demonstrate additional complexity in this prototypical roaming reaction, which we expect to be general. They also provide detailed benchmarks for predictive theories of roaming., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Objectives: The aim was to investigate which factors influence the situational motivation of medical specialists and how situational and contextual motivation affect one another., Methods: A qualitative design was used, and a constructivist approach was adopted with the Self-Determination Theory of motivation as a framework. Twenty-two medical specialists from three medical centers in the Netherlands were recruited through convenience, snowball and purposive sampling and observed for two days each. At the end of the second observation day, a semi-structured interview was conducted. Data were transcribed and coded in an open manner. Themes were finalized through discussion and consensus., Results: Two-hundred and fifty hours of observation data together with the interview data identified that medical specialists experience six main themes influencing their situational motivation during a workday. Technical issues are influencing motivation negatively factors. Working with colleagues can be both a motivating factor and influence motivation negatively, e.g., filling in for each other through feelings of relatedness was motivating. Being in control of one's own planning through feelings of autonomy was motivating. Patient care, especially in combination with teaching, stimulated specialists' motivation., Conclusions: The results indicate that factors influencing motivation negatively are mainly tasks and organizational processes that distract from patient care or that compromise the quality of care. When optimizing the work environment of medical specialists, autonomous motivation and continuing professional development are stimulated.  These, in turn, can improve the quality of patient care and wellbeing of specialists.

The hydrogen-atom adduct with anthracene, 9-dihydroanthracenyl radical (C 14 H 11 ), and its deuterated analogue have been identified by laser spectroscopy coupled to time-of-flight mass spectrometry, supported by time-dependent density functional theory calculations. The electronic spectrum of 9-dihydroanthracenyl radical exhibits an origin band at 19115 cm -1 and its ionization energy was determined to be 6.346(1) eV. The spectra reveal a low-frequency vibrational progression corresponding to a mode described by a butterfly inversion. In the deuterated analogue, a zero-point-energy imbalance along this coordinate is found to lead to a doubling of the observed spectral lines in the progression. This is attributed to quantum-induced symmetry breaking as previously observed in isotopologues of CH 5 + .

The first experimental observation of the primary photochemical channel of acetaldehyde leading to the formation of ketene (CH 2 CO) and hydrogen (H 2 ) molecular products is reported. Acetaldehyde (CH 3 CHO) was photolysed in a molecular beam at 305.6 nm and the resulting H 2 product characterized using velocity-map ion (VMI) imaging. Resonance-enhanced multiphoton ionization (REMPI), via two-photon excitation to the double-well EF 1 Σ state, was used to state-selectively ionize the H 2 and determine angular momentum distributions for H 2 (ν = 0) and H 2 (ν = 1). Velocity-map ion images were obtained for H 2 (ν = 0 and 1, J = 5), allowing the total translational energy release of the photodissociation process to be determined. Following photolysis of CH 3 CHO in a gas cell, the CH 2 CO co-fragment was identified, using Fourier transform infrared spectroscopy, by its characteristic infrared absorption at 2150 cm -1 . The measured quantum yield of the CH 2 CO + H 2 product channel at 305.0 nm is φ = 0.0075 ± 0.0025 for both 15 Torr of neat CH 3 CHO and a mixture with 745 Torr of N 2 . Although small, this result has implications for the atmospheric photochemistry of carbonyls and this reaction represents a new tropospheric source of H 2 . Quasi-classical trajectory (QCT) simulations on a zero-point energy corrected reaction-path potential are also performed. The experimental REMPI and VMI image distributions are not consistent with the QCT simulations, indicating a non reaction-path mechanism should be considered.

The electronic spectra of the ortho-hydroxycyclohexadienyl radical have been observed following the supersonic expansion of the electric discharge products of phenol and water. Hydrogen atoms, split from water, add to the phenol ring at the ortho position, generating syn and anti rotamers with respect to the hydroxyl group. The D 1 ← D 0 transitions were recorded by resonance-enhanced multiphoton ionization spectroscopy. The spectrum of each isomer was isolated through hole-burning spectroscopy. The assignment and symmetry of the excited state are evaluated through ab initio calculations and are employed to assign each spectrum. Both rotamers are calculated to have a puckered ring in the excited state, leading to C 1 symmetry. The spectrum of the anti isomer is assigned well using this symmetry; however, the syn isomer is assigned better in the C s symmetry of the ground state. We use Duschinsky matrices as a tool for the spectroscopist to determine which point group to use when ab initio calculations are ambiguous.

The products of an electrical discharge containing toluene are interrogated using resonance-enhanced multiphoton ionization and laser-induced fluorescence spectroscopies. A previously unreported electronic spectrum recorded at m/z = 105, with a putative origin band at 26053 cm -1 , is assigned to methyltropyl radical, which appears to be a major product of the toluene discharge, plausibly arising from CH insertion. All three o-, m-, and p-xylyl isomers are also identified. These isomers are detected in electrical discharges containing various xylenes, where it is also found that interconversion occurs: A discharge of o-xylene produces some m-xylyl; a discharge of m-xylene produces some o-xylyl; and a discharge of p-xylene produces all three isomers. No α-methylbenzyl was detected, but styrene was. These observations are supported by state-of-the-art quantum chemical calculations, which reveal an isomerization pathway between methyltropyl and xylyl radicals for which there is no analogue in the canonical tropyl-benzyl isomerization.

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 dynamics of CO production from photolysis of H 2 CO have been explored over a 8000 cm -1 energy range (345 nm-266 nm). Two-dimensional ion imaging, which simultaneously measures the speed and angular momentum distribution of a photofragment, was used to characterise the distribution of rotational and translational energy and to quantify the branching fraction of roaming, transition state (TS), and triple fragmentation (3F) pathways. The rotational distribution for the TS channel broadens significantly with increasing energy, while the distribution is relatively constant for the roaming channel. The branching fraction from roaming is also relatively constant at 20% of the observed CO. Above the 3F threshold, roaming decreases in favour of triple fragmentation. Combining the present data with our previous study on the H-atom branching fractions and published quantum yields for radical and molecular channels, absolute quantum yields were determined for all five dissociation channels for the entire S 1 ←S 0 absorption band, covering almost 8000 cm -1 of excitation energy. The S 0 radical and TS molecular channels are the most important over this energy range. The absolute quantum yield of roaming is fairly constant ∼5% at all energies. The T 1 radical channel is important (20%-40%) between 1500 and 4000 cm -1 above the H + HCO threshold, but becomes unimportant at higher energy. Triple fragmentation increases rapidly above its threshold reaching a maximum of 5% of the total product yield at the highest energy.

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.

The photodissociation dynamics of acetone (CH 3 ) 2 CO, cooled in a molecular beam, have been explored over the wavelength range 266-312 nm. Nascent CH 3 fragments were detected by resonance-enhanced multiphoton ionization, followed by mass-selected ion imaging. For photolysis at λ = 306 nm, the image shows a sharp ring, which, when converted to a translational energy distribution, reveals a narrow Gaussian peak with a maximum at 90% of the available energy. As the photolysis energy is increased, the distribution slowly broadens and shifts to higher recoil translational energy. The fraction of available energy in translation energy decreases in favour of internal energy of the CH 3 CO fragment. These observations are consistent with a dynamical model in which the energy of the exit channel barrier on the T 1 surface evolves mostly into relative translational energy. Energy in excess of the barrier is partitioned statistically into all degrees of freedom. No evidence was found for any other dynamical pathway producing CH 3 fragments, including reaction on S 0 or S 1 , for dissociation between 306 and 266 nm. For λ > 306 nm, a diffuse, slow recoil component to the image appears. The translational energy distribution for this component is fit well by a statistical prior distribution of energy. We attribute this component to dissociation on the S 0 , ground state surface; to our knowledge, this is the first direct observation of this channel. The appearance of S 0 dynamics and the disappearance of the T 1 component are consistent with previously inferred barrier height on T 1 for the production of CH 3 CO + CH 3 . The possible atmospheric implications of our findings are discussed.

The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge. The (1 + 1') resonance-enhanced multiphoton ionization (REMPI) spectra of the reaction products, at m/z = parent + 1, or parent + 2 amu, were measured by scanning the first (resonance) laser. The resulting spectra are highly structured. Ionization energies were measured by scanning the second (ionization) laser, while the first laser was tuned to a specific transition. Theoretical calculations, benchmarked to the well-studied H + benzene → cyclohexadienyl radical reaction, were performed. The spectrum arising from the reaction of H + phenol is attributed solely to the ortho-hydroxy-cyclohexadienyl radical, which was found in two conformers (syn and anti). Similarly, the reaction of H/D + toluene formed solely the ortho isomer. The preference for the ortho isomer at 100-200 K in the molecular beam is attributed to kinetic, not thermodynamic effects, caused by an entrance channel barrier that is ∼5 kJ mol(-1) lower for ortho than for other isomers. Based on these results, we predict that the reaction of H + phenol and H + toluene should still favour the ortho isomer under elevated temperature conditions in the early stages of combustion (200-400 °C).

A 71-year-old male was admitted to our hospital with heart failure, cachexia and biochemical disturbances due to a diet consisting of exclusively vegetables, oil and water. Our investigations showed that this diet was a consequence of an excessive preoccupation with health. The patient did not meet criteria for an eating disorder or other DSM-IV psychiatric disorder. We conclude that malnutrition due to health fad diets may be an underestimated medical problem. There is no specific psychopathological disorder that covers this behaviour, and there is no knowledge of its epidemiology. Popular literature is paying a great deal attention to orthorexia nervosa, an alleged eating disorder that describes a pathological obsession with healthy food. In medical literature this concept has been largely neglected, although eating disorder specialists frequently observe this behaviour in their practice. More clinical and scientific attention for this phenomenon is necessary to determine its epidemiology, validity and clinical picture.

We report the observation of a new band system of C2, namely, the 4(3)Πg-a(3)Πu system. The bands, observed by resonant 2-photon ionization spectroscopy and time-of-flight mass spectrometry, were identified through a synergy of high-level ab initio computation and double-resonance spectroscopy. Two bands are firmly identified, 1-3 and 0-2, allowing the 4(3)Πg origin to be placed at 51496.44 cm(-1). The 4(3)Πg state is characterized as having a single bond, with a vibrational frequency of about 1268 cm(-1), and an equilibrium bond length of 1.57 Å. The state is predicted to exhibit a barrier to dissociation, with a rotational constant that unusually increases with vibrational excitation up to a maximum before decreasing at higher vibrational excitation. The new band system allows us to probe the a(3)Πu state of C2 through a straightforward 1 + 1 REMPI scheme.

Excitation spectra of the 1H-naphthalene (1-C10H9) and 1D-naphthalene (1-C10H8D) radicals, and their cations, are obtained by laser spectroscopy and mass spectrometry of a skimmed free-jet expansion following an electrical discharge. The spectra are assigned on the basis of density functional theory calculations. Isotopic shifts in origin transitions, vibrational frequencies and ionization energies were found to be well reproduced by (time-dependent) density functional theory. Absolute bond dissociation energies, ionization energies and proton affinities were calculated using high-level quantum chemical methods.

The ionization energies for three resonance-stabilized radicals are determined: cyclohexadienyl, 1-phenylpropargyl, and methylcyclohexadienyl. The recommended ionization energies are, respectively, 6.820(1), 6.585(1), and 7.232(1) eV. That of cyclohexadienyl is found to be just 0.02 eV above a high level ab initio calculation [Bargholz, A.; Oswald, R.; Botschwina, P. J. Chem. Phys. 2013, 138, 014307], and that of 1-phenylpropargyl is found within the stated error of a recent experimental determination [Holzmeier, F.; Lang, M.; Hemberger, P.; Fischer, I. ChemPhysChem 2014, DOI: 10.1002/cphc.201402446]. The ionization energy of the methylcyclohexadienyl radical is consistent with the ortho isomer. Ionization energies of a range of isotopologues of cyclohexadienyl radical are given, along with their D1 ← D0 origin band positions, which indicate a blue shift of 18 cm(-1) per deuterium atom substituted. The ionization energy of cyclohexadienyl, along with the calculated bond dissociation energy of Bargholz et al., affords a new estimate of the 0 K proton affinity of benzene: 739.7 ± 2.0 kJ/mol. The ionization energies are discussed in terms of the interplay between radical and cation stabilization energies.

The 9-anthracenylmethyl (C15H11) and 1-pyrenylmethyl (C17H11) radicals were identified by a combination of mass-resolved laser spectroscopy of a jet-cooled electrical discharge and quantum chemical methods. The 9-anthracenylmethyl radical was found to exhibit an origin band at 13757 cm(-1), with vibrational structure observed in a1 modes, and even quanta of b1 and a2 modes. The 1-pyrenylmethyl radical was found to exhibit an origin band at 13,417 cm(-1), with a more complex vibrational structure as compared to 9-anthracenylmethyl, on account of its lower symmetry and larger size. The origin bands of these species were predicted to within 250 cm(-1) by fitting a linear relationship between observed origin wavelengths of similar chromophores and the calculated TD-B3LYP transition energies. A refined fit including the title radicals provides estimated absorption energies for the larger 2-perylenylmethyl and 6-anthanthrenylmethyl species of 1.44 and 1.41 eV, respectively, with an estimated error of 30 meV.

The photodissociation dynamics of H2CO molecules at energies bracketing the triple fragmentation threshold were investigated using velocity map ion imaging of the H-atom fragments. An algorithm was developed to model the experimental results as a two-step process: initially barrierless C-H bond fission on the S0 potential energy surface to form H + HCO, followed by secondary fragmentation of those HCO radicals with sufficient internal energy to overcome the small exit channel barrier on the HCO surface to form H + CO. Our model treats the first step using phase space theory (PST) and the second using a combined PST-impulsive model, with a tunneling correction. Experimentally, triple fragmentation reaches 25% of the radical (H + HCO) channel photochemical yield at energies about 1500 cm(-1) above the barrier for breaking the second bond. In addition, the triplet (T1) channel appears to reduce in importance after the barrier on the T1 surface is exceeded, slowly decreasing to <10% of the total radical yield at higher energy. The double PST-impulsive model provides a good fit to the experimental H-atom speed and energy distributions for H2CO dissociation on S0 spanning >7000 cm(-1) of available energy.

The excitation spectra of jet-cooled 4-phenylbenzyl and 4-(4'-methylphenyl)benzyl radicals have been identified by a combination of resonant two-color two-photon ionization mass spectrometry and quantum chemical methods. Both radicals exhibit progressions in the biphenyl torsional mode, peaking near ν = 17. The lowest observed peak for 4-phenylbenzyl was observed at 18598 cm(-1) and is estimated to be the ν = 3 of the progression, while the lowest observed peak for the 4-(4'-methylphenyl)benzyl radical was observed at 18183 cm(-1) and is possibly the origin. The spectra are discussed and compared to other biphenyl and benzyl chromophores.

The spectra of 1-indanyl-based resonance-stabilized radicals containing a hydroxyl group are identified in an electrical discharge containing indene and its alkylated derivatives. It is argued that such species form by addition of a discharge-nascent hydroxyl radical, formed from trace water, to the π bond on the five-membered ring of the parent molecule. The spectral carriers are identified by analysis of their excitation and emission spectra guided by the results from quantum chemical calculations. All three hydroxylated radicals are found to exhibit origin bands in the 21300 cm(-1) region: the 2-hydroxy-indan-1-yl radical at 21364 cm(-1), the 2-hydroxy-2-methyl-indan-1-yl radical at 21337 cm(-1), and the 2-ethyl-2-hydroxy-indan-1-yl radical exhibiting two origins of similar intensity at 21287 and 21335 cm(-1).

Background: Obsessive-compulsive disorder (OCD) is a chronic, psychiatric disease which can be highly resistant to treatment. Several studies have suggested that family factors may play a role in the etiology and course of OCD., Aim: To provide an overview of current knowledge about the complex interaction between OCD and family factors., Method: We performed a systematic search of the literature, using PubMed and Psychinfo., Results: OCD places a heavy burden on partners and family members, and their responses to symptoms influence the course of the disease, particularly the effect of cognitive behavioural therapy (CBT). Interventions aimed at improving communicative skills and creating a more balanced family response can have a positive influence on the course of OCD., Conclusion: It is advisable to integrate family factors into the treatment of OCD. Further research on this topic is needed.

After benzene and naphthalene, the smallest polycyclic aromatic hydrocarbon bearing six-membered rings is the threefold-symmetric phenalenyl radical. Despite the fact that it is so fundamental, its electronic spectroscopy has not been rigorously scrutinized, in spite of growing interest in graphene fragments for molecular electronic applications. Here we used complementary laser spectroscopic techniques to probe the jet-cooled phenalenyl radical in vacuo. Its spectrum reveals the interplay between four electronic states that exhibit Jahn-Teller and pseudo-Jahn-Teller vibronic coupling. The coupling mechanism has been elucidated by the application of various ab initio quantum-chemical techniques.

Gas phase excitation and emission spectra of three naphthylmethyl radical chromophores are presented. These resonance-stabilized species, 1-naphthylmethyl, 2-naphthylmethyl, and α-acenaphthenyl, each possessing an sp(2) carbon adjacent to a naphthalene moiety, are studied by resonant two-color two-photon ionization, laser induced fluorescence, and dispersed fluorescence spectroscopy. Identification of the radicals is made through a combination of dispersed fluorescence and density functional theory calculations. All three species possess spectra in the 580 nm region. The possible relevance to unidentified spectroscopic features such as the diffuse interstellar bands and emission from the Red Rectangle nebula is discussed.

The electronic spectrum of the jet-cooled 1-indanyl radical has been identified in the products of a hydrocarbon discharge in argon. Electronic excitation spectra were observed in the region 20800-22600 cm(-1) by resonant two-color two-photon ionization and laser-induced fluorescence spectroscopies. In addition to the new spectrum at m/z = 117, the spectrum of 1-phenylpropargyl was also observed strongly, as was an unidentified spectrum carried by m/z = 133. The origin band of the 1-indanyl A2A''-X2A'' band system was observed at 21159 cm(-1) with the ionization potential of the radical experimentally determined to be 6.578 +/- 0.001 eV from a photoionization efficiency spectrum. Single vibronic level fluorescence was dispersed to determine the ground state vibrational frequencies that were utilized to confirm the identity of the radical in comparison with quantum chemical calculations. The calculated ground state frequencies and ionization potential, along with a calculated dispersed fluorescence spectrum of the origin band for the 1-indanyl radical, all provide a positive chemical identification.

The cis-1-vinylpropargyl (cis-1VPR, cis-pent-4-en-1-yn-3-yl) and trans-1-vinylpropargyl (trans-1VPR, trans-pent-4-en-1-yn-3-yl) radicals, produced in a supersonically cooled hydrocarbon discharge, have been identified by a synergy of 2-dimensional fluorescence and ionization spectroscopies, revealing their electronic origin transitions at 21,232 and 21,645 cm(-1) respectively. These assignments are supported by an excellent agreement between calculated ground state frequencies of cis-1VPR and trans-1VPR with those obtained by dispersed fluorescence spectroscopy. In addition, high-resolution rotational contours of the two bands are well simulated using calculated X- and A-state trans-1VPR and cis-1VPR rotational constants. Finally, computed origin transition energies of these two isomers are within several hundred wavenumbers of the observed band positions. With the 1-phenylpropargyl radical, the 1VPR isomers are the second 1-substituted propargyl species to have been observed abundantly from a hydrocarbon discharge, while no 3-substituted analogue has been positively identified. This is likely due to the greater resonance stabilization energy of the 1-substituted species, arising from concerted delocalization of the unpaired electron over the vinyl and propargyl moieties.

We report studies aimed at unraveling the complicated structure of the CCl 2 A (1)B 1 <-- X (1)A 1 system. We have remeasured the fluorescence excitation spectrum from approximately 17,500 to 24,000 cm (-1) and report the term energies and A rotational constants of many new bands for both major isotopologues (C (35)Cl 2, C (35)Cl (37)Cl). We fit the observed term energies to a polyad effective Hamiltonian model and demonstrate that a single resonance term accounts for much of the observed mixing, which begins approximately 1300 cm (-1) above the vibrationless level of the A (1)B 1 state. The derived A (1)B 1 vibrational parameters are in excellent agreement with ab initio predictions, and the mixing coefficients deduced from the polyad model fit are in close agreement with those derived from direct fits of single vibronic level (SVL) emission intensities. The approach to linearity and thus the Renner-Teller (RT) intersection is probed through the energy dependence of the A rotational constant and fluorescence lifetime measurements, which indicate a barrier height above the vibrationless level of the X (1)A 1 state of approximately 23,000-23,500 cm (-1), in excellent agreement with ab initio theory.

The gas-phase laser-induced fluorescence (LIF) spectrum of a 1-phenylpropargyl radical has been identified in the region 20,800-22,000 cm(-1) in a free jet. The radical was produced from discharges of hydrocarbons including benzene. Disregarding C2, C3, and CH, this radical appears as the most strongly fluorescing product in a visible wavelength two-dimensional fluorescence excitation-emission spectrum of a jet-cooled benzene discharge. The structure of the carrier was elucidated by measurement of a matching resonant two-color two-photon ionization spectrum at m/z = 115 and density functional theory. The assignment was proven conclusively by observation of the same excitation spectrum from a low-current discharge of 3-phenyl-1-propyne. The apparent great abundance of the 1-phenylpropargyl radical in discharges of benzene and, more importantly, 1-hexyne may further underpin the proposed importance of the propargyl radical in the formation of complex hydrocarbons in combustion and circumstellar environments.

A two-dimensional fluorescence (excitation/emission) spectrum of C2 produced in an acetylene discharge was used to identify and separate emission bands from the d (3)Pi(g)<--c (3)Sigma(u) (+) and d (3)Pi(g)<--a (3)Pi(u) excitations. Rotationally resolved excitation spectra of the (4<--1), (5<--1), (5<--2), and (7<--3) bands in the d (3)Pi(g)<--c (3)Sigma(u) (+) system of C2 were observed by laser-induced fluorescence spectroscopy. The molecular constants of each vibrational level, determined from rotational analysis, were used to calculate the spectroscopic constants of the c (3)Sigma(u) (+) state. The principal molecular constants for the c (3)Sigma(u) (+) state are B(e)=1.9319(19) cm(-1), alpha(e)=0.018 55(69) cm(-1), omega(e)=2061.9 cm(-1), omega(e)x(e)=14.84 cm(-1), and T(0)(c-a)=8662.925(3) cm(-1). We report also the first experimental observations of dispersed fluorescence from the d (3)Pi(g) state to the c (3)Sigma(u) (+) state, namely, d (3)Pi(g)(v=3)-->c (3)Sigma(u) (+)(v=0,1).