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Given its abundance in the interstellar medium recently justified by astronomical observations, the chemistry and reactivity of the metal-bearing molecule MgS require special attention. The availability of up-to-date collision data between this MgS molecule and the most abundant perturbing species H |$_2$| and He in the interstellar medium is an essential resource to derive reliable values of its molecular abundance from astronomical observations. This work aims to provide improved scattering parameters for the MgS molecular system in collision with He. A new 2D potential energy surface (2D-PES) is derived by adopting the state-of-the-art level of theory of the explicitly correlated coupled cluster with single, double, and perturbative triple excitations (RCCSD(T)-F12) method in conjunction with the aug-cc-pVTZ basis sets. This PES was used to calculate inelastic cross-sections within the framework of the close-coupling (CC) theory for total energies |$\le 500$|  cm |$^{-1}$| and J |$\le 21$|⁠. Using the Maxwell–Boltzmann distribution of kinetic energies, these cross-sections were integrated to generate the collisional (de)-excitation rate coefficients for temperatures below 100 K. We expect that the new rate coefficients will help us to analyse present and future observations of this key molecule for the interstellar chemistry. [ABSTRACT FROM AUTHOR]

The cyclic form of magnesium dicarbide molecule (c-MgC |$_2$|⁠) has been detected in the carbon-rich circumstellar envelope of IRC+10216 and is considered as a valuable tracer for characterizing the physical conditions of the surrounding gas. In order to make the most of c-MgC |$_2$| observations and accurately derive the physical conditions of the media where c-MgC |$_2$| is detected, radiative transfer modelling, including collisional and radiative (de-)excitations, have to be performed. Here, we study the excitation of c-MgC |$_{2}$| induced by collisions with He (as a proxy for H |$_2$|⁠). A new 3D potential energy surface (PES) is constructed using highly correlated ab initio methods. This PES reveals a minimum with a well depth of 20.66 cm |$^{-1}$| below the c-MgC |$_2$| -He dissociation limit. Using this PES, we compute excitation cross sections for transitions between the low-lying rotational energy levels of c-MgC |$_2$| using the time-independent quantum mechanical close-coupling formalism. These cross sections are then thermally averaged over a Boltzmann energy distribution in order to derive excitation rate coefficients at low temperatures (⁠|$T \le 30$|  K). To evaluate the impact of these new rate coefficients on the interpretation of c-MgC |$_2$| observational spectra, we perform radiative transfer calculations. We find that a very high gas density (⁠|$n \gt 10^6$| cm |$^{-3}$|⁠) is needed in order for the collisional excitation to compete with the radiative de-excitation. We also find that the excitation temperatures of the observed lines predicted by our model differ by a factor two from the value derived from the observations in IRC+10216 circumstellar envelope, indicating that the excitation of c-MgC |$_{2}$| may also be driven by a strong radiative pumping in such media. Therefore, a more sophisticated non-LTE modelling, that takes into account the collisional and radiative excitations as well as the radiative pumping, is required to accurately interpret the observational spectra of c-MgC |$_2$|⁠. [ABSTRACT FROM AUTHOR]

For a better understanding of the physico-chemistry in the interstellar medium, collisional data are needed. In this work, we provide rate coefficients for the recently detected by Cabezas and collaborators in 2023 sodium cyanoacetylide molecule NaC |$_{3}$| N(⁠|$X^{1}\Sigma ^{+}$|⁠) induced by collisions with He. A new two-dimensional potential energy surface (2D-PES) is derived by adopting the high-level theory of the explicitly correlated coupled cluster with single, double, and perturbative triple excitations (CCSD(T)-F12) in conjunction with the aug-cc-pVTZ basis sets. Our 2D-PES presents two minima: the global one with a well depth of |$-86.58$|  cm |$^{-1}$| and the second well with a |$-47.01$|  cm |$^{-1}$| depth. This was expected by the Natural Bond Orbital analysis showing two electrophilic zones located on Na and N linked Carbon with respective atomic charges : |$+0.96575$| and |$+0.28910$|⁠. This PES was used to calculate inelastic cross-sections within the framework of the close-coupling theory for total energies |$\le 170$|  cm |$^{-1}$| and |$J\le 22$|⁠. Using the Maxwell–Boltzmann distribution of kinetic energies, these cross-sections were integrated to generate the collisional (de)-excitation rate coefficients for temperatures below 30 K. In order to estimate the impact of the computed collisional rates, a non-local thermodynamical equilibrium radiative transfer calculation was performed. The new collisional data can allow accurate NaC |$_{3}$| N abundance determination in the interstellar medium. [ABSTRACT FROM AUTHOR]

Determining physical conditions in interstellar environments requires reliable estimation of collisional data for molecules detected in space. In this work, we report a rate coefficients calculation of MgC3N(X 2Σ+) induced by collision with He. This study is based on a new 2D potential energy surface (2D-PES), obtained from the explicitly correlated restricted open-shell coupled cluster approach with single, double, and perturbative triple excitation (rccsd(t)-f12) and the aug-cc-pVTZ basis sets. The MgC3N–He PES presents a global minimum with a well depth of −45.6 cm−1. Based on this interaction potential, we derived the excitation cross-sections using the close-coupling quantum time-independent formalism for total energies ≤500 cm−1 and N ≤ 40. These cross-sections were then integrated on a Maxwell–Boltzmann distribution of kinetic energies to obtain the collisional (de)-excitation rate coefficients for thermal temperature below 100 K. A non-LTE radiative transfer calculation was performed using the present collisional rates in order to estimate their impact on the abundance of MgC3N. These collisional data can help astronomers for the detection and an accurate determination of MgC3N abundance in the investigated interstellar clouds. [ABSTRACT FROM AUTHOR]

Collisional excitation of C5H+ by He was performed by mean of state-of-the-art methods. A high level of theory quantum chemical calculations were made to determine the interaction potential energy surface of C5H+ with helium. The new two-dimensional potential energy surface obtained from the RCCSD(T)-F12 ab initio approach associated with aug-cc-pVTZ basis sets, presents two minima below its dissociation limit with well depths of |$-101.8$| and |$-100.2\, \mathrm{cm}^{-1}$|. In order to derive accurate physical conditions from rotational transitions of the recently discovered C5H+ molecule in Taurus molecular cloud (TMC-1), rate coefficients calculations are performed. The C5H+(X1Σ+)–He de-excitation rates are obtained after averaging cross-sections for thermal temperature below 100 K. The integral cross-sections are computed with the close-coupling quantum time-independent formalism for |$E\le 520 \, \mathrm{cm}^{-1}$| and J ≤ 15. The new collisional data will allow accurate determination of the C5H+ abundance and will help to understand the chemistry of carbon chain ions in the interstellar gas. [ABSTRACT FROM AUTHOR]

Tricarbon and pentacarbon monoxides have been detected towards the Taurus Molecular Cloud (TMC-1) with relatively important abundances. Understanding the chemical formation of these molecules requires interpreting their observational spectra by mean of non-local thermodynamical equilibrium modelling. For this purpose, we report rate coefficients of  C3O and  C5O induced by collision with He for temperatures up to 100 K. These data are obtained by calculating inelastic cross sections for the 31 low-lying rotational levels of  C3O and  C5O using the close-coupling approach. The comparison of the new rate coefficients with those of HC3N and HC5N, previously used to interpret the observational spectra of  C3O and  C5O, reveals differences of up to an order of magnitude. The effect of the new collisional rate coefficients in radiative transfer calculations is checked by computing the excitation temperatures for some transitions and simulating the  C3O and  C5O column densities observed towards TMC-1. Our findings suggest that the use of HC n N as template for C n O may lead to local thermodynamic equilibrium conditions for gas densities as low as ∼103  cm−3. Regarding the interpretation of the observational spectra, using radiative transfer modelling based on the actual C n O collisional rate coefficients instead of rotational diagram analysis leads to underestimate the column densities reported in the literature by up to 25 per cent and accordingly the  C3O/ C5O abundance ratio by up to 50 per cent. We expect that the new rate coefficients and the radiative transfer calculations presented in this work will encourage further modellings of the C n O abundance and accordingly constrain the chemistry. [ABSTRACT FROM AUTHOR]

The CCN radical has been recently detected in the interstellar medium. Accurate modeling of its abundance in such media requires one to model its excitation by both radiation and collisions. Here, we report the first quantum mechanical close-coupling study of CCN—He collisions. Calculations of fine-structure resolved excitation cross sections of CCN(X2Π) induced by collision with He are performed for kinetic energies below 500 cm−1. The calculations are based on new two-dimensional potential energy surfaces obtained from coupled cluster approaches. We found that the inelastic cross sections for spin-orbit conserving transitions are larger than those for spin-orbit changing transitions. The new collisional data should significantly help the interpretation of interstellar CCN emission lines observed with current and future telescopes and we expect that they will allow accurate determination of the CCN abundance in the interstellar medium, which is crucial to understand the chemistry of carbon chain species in the interstellar gas. [ABSTRACT FROM AUTHOR]

Collisional energy transfer under cold conditions is of great importance from the fundamental and applicative point of view. Here, we investigate low temperature collisions of the SH- anion with He. We have generated a three-dimensional potential energy surface (PES) for the SH-(X¹Σ+)-He(¹S) van der Waals complex. The ab initio multi-dimensional interaction PES was computed using the explicitly correlated coupled cluster approach with simple, double, and perturbative triple excitation in conjunction with the augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. The PES presents two minima located at linear geometries. Then, the PES was averaged over the ground vibrational wave function of the SH- molecule and the resulting two-dimensional PES was incorporated into exact quantum mechanical close coupling calculations to study the collisional excitation of SH- by He. We have computed inelastic cross sections among the 11 first rotational levels of SH- for energies up to 2500 cm-1. (De-)excitation rate coefficients were deduced for temperatures ranging from 1 to 300 K by thermally averaging the cross sections. We also performed calculations using the new PES for a fixed internuclear SH- distance. Both sets of results were found to be in reasonable agreement despite differences existing at low temperatures confirming that accurate predictions require the consideration of all internal degrees of freedom in the case of molecular hydrides. The rate coefficients presented here may be useful in interpreting future experimental work on the SH- negative ion colliding with He as those recently done for the OH- -He collisional system as well as for possible astrophysical applications in case SH- would be detected in the interstellar medium. [ABSTRACT FROM AUTHOR]

In order to derive accurate physical conditions of the interstellar clouds (such as TMC-1) from the rotational transitions of C2O, collisional rates are needed. Based on a new two-dimensional potential energy surface (PES), we report a new rate coefficients calculation of C2O(X 3Σ−) induced by collision with He. This PES was obtained from the explicitly correlated restricted open-shell coupled cluster with single, double, and perturbative triple excitation (rccsd(t)-f12) ab initio approach associated with aug-cc-pVTZ basis sets. The C2O–He PES presents one minimum below its dissociation limit with a well depth of 42.376 cm−1. The close-coupling quantum time-independent formalism was used to derive cross sections for E ≤ 370 cm−1 and N ≤ 10. De-excitation rate coefficients are obtained for thermal temperature below 80 K. [ABSTRACT FROM AUTHOR]

To determine the chemical composition of gases in molecular clouds, the oxygen-bearing systems C n O are needed as probe elements. The pentacarbon monoxide C5O was recently detected in TMC-1, and in order to derive accurate physical conditions from its rotational transitions, calculation of rate coefficients of C5O(1Σ+) induced by collision with He are performed for thermal temperature below 100 K. These calculations are based on a new 2D potential energy surface (2D-PES) obtained from the explicit correlated coupled cluster with single, double, and pertubative triple excitation (ccsd(t)-f12) ab initio approach associated with aug-cc-pVTZ basis sets. The C5O–He PES presents two minima below its dissociation limit with a well depths of −59.321 and −53.059 cm−1. By mean of this PES, the integral cross sections are calculated in the close-coupling quantum time independant formalism for |$E\le 500 \, {\rm cm}^{-1}$| and J ≤ 20. The de-excitation rate coefficients are obtained after averaging these cross sections at low temperatures. We expect that the new collisional data will allow accurate determination of the C5O abundance in the interstellar medium, as well as the interpretation of its emission lines. These new data are crucial to understand the chemistry of carbon chain species in the interstellar gas. [ABSTRACT FROM AUTHOR]

Using Fourier transform spectrometer, He-broadening coefficients in the 2 v 2 0 and 3 v 2 1 − v 2 1 bands of carbonyl sulfide (16O12C32S) have been measured for the first time in the P- and R-branches. Measurements have been performed at room temperature (295 K) for 200 ro-vibrational lines with rotational quantum number ranging from 1 ≤ J ≤ 64, using a mono-spectrum non-linear least squares fitting of Voigt profiles. The measured values were discussed as a function of the rotational quantum number and compared to previous data. These broadening coefficients were also calculated on the basis of Robert and Bonamy's formalism using an ab-initio potential energy surface (PES). In addition, we have measured pressure shift coefficients for 92 transitions in both bands, these results were compared with those of the 2ν3 band. The line intensities in the 2 v 2 0 and 3 v 2 1 − v 2 1 bands were also retrieved using the same spectra. The analysis of these intensities allows us to derive a consistent set of line intensity parameters such as vibrational transition moments, band intensities as well as Herman-Wallis (HW) coefficients. [ABSTRACT FROM AUTHOR]

An appropriate estimation of the abundance of the observed C5 radical in the interstellar medium requires accurate radiative and collisional rate coefficients. We present the first two-dimensional potential energy surface (2D-PES) for the ground electronic state of the C5(X1Σ+)–He(X1S) van der Waals system, obtained using an explicitly correlated coupled-cluster method with single, double, and perturbative triple excitations (RCCSD(T)-F12). This PES is subsequently used in quantum close-coupling (CC) scattering calculations. Collisional excitation cross-sections of the rotational levels of C5 by He were calculated for energies up to 1500 cm−1 using the standard (CC) method. The thermal dependence of the corresponding rate coefficients is given for the low and moderate temperature T ≤ 300 K regime of interstellar molecular clouds. This is the first study on the collisional rate coefficients for this system and may have important implications for the astrophysical detection of C5(X1Σ+) and modeling of carbon-rich media. [ABSTRACT FROM AUTHOR]

Despite that the tricarbon monosulfide (C3S) is among the first sulfur-containing carbon-chain molecules to be detected in the interstellar medium, no studies focused on the determination of its collisional rates. These rate coefficients are essential to estimate the abundance of C3S in the interstellar medium. Computations of the C3S( Σ + 1 ) downward rate coefficients, induced by collision with He, are performed by averaging the integral cross sections at low temperature (below 25 K ). Calculations of the cross sections in the close-coupling quantum time independent formalism for E c ≤ 110 cm − 1 and J ≤ 10 are based on a new 2-D potential energy surface. This PES is obtained from the explicit correlated coupled cluster with a single, double and perturbative triple excitation [ccsd(t)-f12] ab initio approach and the aug-cc-pVTZ basis sets. The PES have a global minimum of − 55.69 cm − 1 located at R = 6.25 bohr and θ = 94 ∘ , and a second minimum of − 36.95 cm − 1 at R = 9.35 bohr and θ = 0 ∘ . A comparison of C3S rates with those of the isoelectronic molecule C3O was made. The results indicate a great temperature dependence of the rates for transitions of Δ J > 2 . We expect that the new collisional data will allow for accurate determination of the C3S abundance in several interstellar regions. [ABSTRACT FROM AUTHOR]

The C5S molecule is the largest member of the series of sulphur-containing carbon chains C n S observed in space. Given the lack of data concerning this molecule, we computed rate coefficients of C5S(1Σ+) induced by collision with He. These rates are obtained for thermal temperature below 100 K by mean of a new two-dimensional potential energy surface (PES) calculated with the explicit correlated coupled cluster with single, double, and pertubative triple excitation (ccsd(t)-f12) ab initio approach and the aug-cc-pVTZ basis sets. The C5S–He PES presents three minimums of −59.726, −55.355, and −36.506 cm−1 below its dissociation limit. Using this PES, the integral cross-sections are performed in the close-coupling (CC) and coupled-state (CS) quantum time independent formalisms for |$E_\mathrm{ c}\le 500 \, \mathrm{ cm}^{-1}$| and J ≤ 13 (for CC) and J ≤ 50 (for CS). By averaging these cross-sections we obtained the downward rate coefficients. The new collisional data are used to simulate the excitation of C5S in the circumstellar gas. We obtain the excitation and brightness temperatures of the four lines observed towards the IRC+10216 which confirms the necessity of using radiative transfer calculations to accurately determine C5S abundance since the local thermodynamic equilibrium conditions are not fulfilled. The new collisional data should help to estimate the abundance of C5S in several interstellar regions. [ABSTRACT FROM AUTHOR]

Among all the molecular species found in the interstellar medium, molecules with threefold symmetry axes play a special role, as their rotational spectroscopy allows them to act as practical gas thermometers. Methyl-cyanide (CH3CN) is the second most abundant of those (after ammonia). We compute in this paper the collisional dynamics of methyl-cyanide in collision with helium, for both the A- and the E-symmetries of CH3CN. The potential energy surface is determined using the CCSD(T)-F12b formalism and fit with convenient analytic functions. We compute the rotationally inelastic cross sections for all levels up to 510 cm−1 of collision energy, employing at low energy exact Coupled Channels methods, and at higher energies, approximate Coupled States methods. For temperatures from 7 K up to 300 K, rates of quenching are computed and most are found to differ from those reported earlier (up to a factor of a thousand), calling for a possible reexamination of the temperatures assigned to low density gasses. [ABSTRACT FROM AUTHOR]

The interaction potential energy surface of the methinoposphide (HCP)-H2 complex is calculated at the ab initio coupled-cluster level of theory with an aug-cc-pVTZ Gaussian basis set. The [H-C] and [C-P] bond lengths of HCP are set to their values at the linear equilibrium ground vibrational level of the molecule. The calculated interaction energy presents two minima located 106.3 and 67.6 cm-1 below the HCP+H2 dissociation limit. Using the interaction potential obtained, we have computed collision excitation cross sections in the close-coupling approach and downward rate coefficients at low temperature, i.e., T≤70 K. These quantities are significantly magnified in comparison with their counterparts for the HCP-He collisions. It is shown that there is a propensity toward ΔJ=1 transitions. [ABSTRACT FROM AUTHOR]

A three-dimensional potential energy surface has been calculated for the ground electronic state of the HOCO+–He system. The calculations were performed at the coupled electron pair approximation level with an extended basis set which ensures a balance between accuracy and feasability. The validity of the method and of the basis set was tested through calculations of the polarizability of the He atom and of the spectroscopic constants of the HOCO+ ion. The calculated potential energy surface has been fitted to a spherical harmonic expansion to facilitate calculations of rotational excitation of HOCO+ by collisions with He.© 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Cyclopropenylidene, c-C3H2, is a simple hydrocarbon, ubiquitous in astrophysical gases, and possessing a permanent electric dipole moment. Its readily observed rotational transitions make it an excellent probe for the physics and history of interstellar matter. The collisional properties of c-C3H2 with the main background gas, H2, are computed here. We present a full 5-D Potential Energy Surface in the rigid molecule approach, and fit it to relevant functionals for subsequent scattering. We perform low-energy quantum scattering at energies less than 50 cm−1. We use both ortho and para H2 as projectiles. We determine the quality of the various approximations to exact coupled channel scattering and examine paths to go towards higher energy scattering relevant for astrophysics. We compare the results obtained here with earlier ones for scattering with helium. [ABSTRACT FROM AUTHOR]

Among the closed-shell hydrocarbons, the carbenes c- and l-C3H2 are the lightest ones to display a permanent electric dipole moment and be detectable by rotational spectroscopy. The cyclic form, cyclopropenylidene, is ubiquitous in the InterStellar Matter (ISM) of the Milky Way and external galaxies. As such, it serves as a marker to help in characterizing the physical conditions of the ISM. The linear form, propadienylidene, is less abundant. In order to get access to their absolute and relative abundances, it is essential to understand their collisional excitation/quenching schemes. We compute here a precise ab initio potential energy surface for the interaction of c- and l-C3H2 with helium, by means of a CCSD(T)-F12a formalism and a fit onto relevant spherical harmonics functions. We conduct quantum dynamical scattering in order to get precise cross sections using a coupled-channel approach for solving the nuclear motion. We average sections to have rates for rotational quenching from 5 to 150 K. We show that these new rates are vastly different, up to more than an order of magnitude, from the older rates presented in the literature, computed with angular momentum algebra only. We expect large differences in the astrophysical analyses of C3H2, including the chemical history of those ubiquitous carbenes. [ABSTRACT FROM AUTHOR]

Neutral and ionic nitrogen sulfide, NS, are closely connected with the chemistry of the larger nitrogen-containing molecular species. NS+ cation was recently detected in some regions of the interstellar medium, where a small abundance is estimated. In order to help for the identification of this cation in other sources, we present the collision rates for the rotational (de-)excitation of NS+ by He. They are obtained using quantum scattering calculations for collision energies between 1.26 and 1400 cm−1, followed by averaging of the cross-sections over a Maxwell–Boltzmann distribution. These quantum nuclear motion treatments are performed on a new 3D potential energy surface (PES) for the NS+(X1Σ+) − He weakly bound complex. This PES is generated in Jacobi coordinates and using the explicitly correlated coupled cluster method (CCSD(T)-F12) in conjunction with the aug-cc-pVTZ basis set. Afterwards, rate constants for rotational levels of NS+ up to 10 and temperatures in the range of 2–300K are deduced. Particularly, the 3–2 transition, recently observed in the surveys, is found to be predominant at very low temperatures, whereas the 5–4 transition is predicted to dominate at higher temperatures, which may be used for the identification of this cation in hot media. The use of the rates of CS colliding with He are viewed to be a good approximation for the estimation of NS+ abundances. [ABSTRACT FROM AUTHOR]

The HNCO-He complex is characterized using explicitly correlated ab initio methodology. We generate its potential energy surface (PES) along the intermonomer Jacobi coordinates. This PES is incorporated later into dynamical computations in order to deduce the rotational excitation cross-sections and coefficient rates of HNCO colliding with He. Calculations of state-to-state cross-sections for transitions among the first 31 rotational levels of HNCO (up to JKaKc = 1019) are performed using the quantum close-coupling scheme for total energies < 100 cm-1 and using the coupled state approach for energies up to 550 cm-1. Rate coefficients for temperatures ranging from 2 to 100 K are calculated by the averaging of the cross-sections over a Maxwell-Boltzmann distribution. A propensity rule towards even ΔJ rotational transition is observed. The present theoretical data are needed for the estimation of the abundance of the astrophysical important HNCO molecule from the surveys. [ABSTRACT FROM AUTHOR]

The potential energy surface is computed at the explicitly correlated coupled cluster with simple, second and perturbative triple excitation method (CCSD(T)–F12) in connection with the augmented–correlation consistent–polarized valence triple zeta (aug–cc–pVTZ) Gaussian basis set for the NeH+ −He system. The calculations were performed by first taking into account the vibration of the molecule and then averaging the so-obtained three-dimensional potential. From this average interaction potential, cross-sections among the 11 first rotational levels of NeH+ induced by collision with He are calculated for energies up to 4000 cm−1 using the quantum mechanical close coupling (CC) approach. Collisional rate coefficients are obtained by thermally averaging these cross-sections at low temperature (T ≤ 300 K). The propensity rules of the rotational transitions obtained in this paper are discussed and compared with those of HeH+ and ArH+ in collision with electron. This work may be helpful for the eventual investigations, both theoretical and experimental, focused to detect the key cationic noble gas hydride NeH+ in the interstellar and circumstellar media as well as in laboratory experiments. [ABSTRACT FROM AUTHOR]

Isocyanic acid (HNCO) is a simple molecule containing the four main atoms essential for life and can be considered as a prebiotic molecule. To model the HNCO emission in the IRAS16293-2422 class 0 low-mass protostar, we used a new set of HNCO collisional coefficients with ortho-H2 and para-H2, computed from a set of rotational excitation quenching rates between HNCO and H2 based on a novel potential energy surface for the rigid molecules interactions. We present here the HNCO Potential Energy Surface used to compute this new set of collisional coefficients and the result of the IRAS16293-2422 HNCO spectrum modelling using them. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the determination of the rotational excitation rate coefficients of the first observed molecule containing noble gas 36ArH+ isotope by He. Hence, we present the first potential energy surface (PES) of ArH+ --He van der Waals system. The interaction PES of the ArH+ (X¹ Σ)+-He(¹S) complex is calculated by the ab initio explicitly correlated coupled cluster with single, double, and perturbative triple excitation (CCSD(T)-F12) method in connection with the augmented correlation consistent triple zeta Gaussian basis (aug-cc-pVTZ). The interaction potential presents two global minima of 708.00 and 172.98 cm-1 below the ArH+ (X¹ Σ +)-He(¹S) dissociation limit. Using the PES obtained, we have computed integral inelastic cross-sections in the close-coupling approach among the first 11 rotational levels of ArH+ for energies up to 2500 cm-1. Downward rate coefficients were determined at low temperature (T ≤ 300 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments. [ABSTRACT FROM AUTHOR]

Blood and body fluid Exposure is a major occupational safety problems for health care workers. Therefor We conducted a descriptive and retrospective study to identify the characteristics of blood exposure accidents in health care settings which lasted five years (2005-2009) at the two university hospitals of Sfax. We have 593 blood exposure accidents in health care settings 152 (25.6%) health personnel and 441 (74.4%) trainees' doctors, nurses and health technicians. The mechanism of blood and body fluid exposure was accidental needle-stick injury in 78.9% of health staff, and 81% of trainees, accidental cut in 14.7% of health workers and 10.2% of trainees. The increasing severity of blood exposure accidents is linked to the lack of safe behavior against this risk. [ABSTRACT FROM AUTHOR]

Aims. The present paper focuses on the calculation of the collision rate coefficients for rotational excitation of the 12CF+ and its isotopologue 13CF+ by He for temperature ranging from 10 to 300 K. Methods. A two-dimentional (2D) potential energy surface (PES) of the CF+(X1Σ+)-He(1S) system is calculated at the ab initio coupled cluster with single, double, and perturbative triple excitation level of theory with the aug-cc-pV5Z basis set. The basis set superposition errors were taken into account in our computation. Dynamical calculations of state-to-state rotational integral cross sections of the CF+ by collision with He were performed using the close-coupling method. Results. The PES presents a global minimum of ∼212 cm-1 below the CF+-He dissociation limit. Collisional cross sections among the first 11 rotational levels of CF+ were calculated for total energies up to 1500 cm-1. Downward rate coefficients between the rotational levels were calculated for temperature ranging from 10 to 300 K. A propensity toward an even parity of ΔJ is observed. [ABSTRACT FROM AUTHOR]

Introduction: In emergency departments, workers regularly report unfavorable working conditions. It's a stressful workplace with excessive workloads, high demands on patient care including exposure to violence, time pressures and overcrowding. Objectives: -Identify the prevalence of violence, psychological distress and job stress in the emergency department. -Investigate risk factors of aggression among emergency department staff. Methods: This study is a descriptive-cross sectional analysis study conducted on emergency department staff. Data were collected through a questionnaire including sociodemographic information, circumstances of the aggression, the Karasek questionnaire, and the GHQ-12 (General Health Questionnaire). Results: Our study included 62 health workers. Half of the population were physicians. The prevalence of assault was estimated at 59.6%. Psychological distress was noted in 64.5% of cases. Occupational stress was estimated at 75.8%. The most common type of assault was verbal aggression (86.4%). The aggressor was most often an accompanying person. The occurrence of violence was not associated with the worker's psychological distress or job stress. On the other hand, we noted an association between aggression and variable work schedule. Conclusions: Violence against healthcare workers in the emergency department is an important phenomenon. Preventive actions should be taken to improve health professional wellbeing at work. [ABSTRACT FROM AUTHOR]

Introduction: Psychosocial risks (PSR) represent a new scourge of risks at work. The direct links between these risks and occupational accidents (OA) are not well documented, but some work restraints such as time pressure are common factors for both stress and accidents. Objectives: To establish a relationship between different PSR perceived by health staff and the occurrence of OA. Methods: Cross-sectional study conducted among staff working at Habib Bourguiba Hospital in Sfax from 1st January to 31 March 2015. The evaluation of mental health was performed by using the validated French version of questionnaire KARASEK. Results: The study involved 326 care staff (115 men and 211 women). The average age was 36 years old. The participants were mainly nurses (30.6%) and trainee physicians (35.6%). Blood exposure accidents were predominant (66.1% of cases) and were associated with high psychological demands at work with OR = 2.539 (95% CI [1.037 - 6.219]). Health care workers had a high psychological demand in 85.3% and a low latitude in 78.8% of cases. According to the Karasek model, tense employees accounted for 68.7% and assets 16.6%. OAs occurring during care were associated with night work and working in the emergency and resuscitation department (OR = 5,772 (95% CI [1,227-27,146] and OR = 5,778 (95% CI [1,702 -19,619]) respectively). Conclusions: The prevention of OA goes through the management of PSR, which remains a major concern for health and safety workers at work via the application of preventive strategies based on in-depth analysis of work situations. [ABSTRACT FROM AUTHOR]