Infrared predissociation vibrational spectroscopy of Li⁺(H2O)(3-4)Ar(0,1) reanalyzed using density functional theory molecular dynamics.

The experimental IR-PD (infrared predissociation) spectra of Li(+)(H2O)(3-4)Ar and Li(+)(H2O)(3-4) clusters, monitoring two different loss channels and thus different temperatures, have been reanalyzed using DFT-MD (density functional theory based molecular dynamics) simulations for finite temperature and anharmonic theoretical spectroscopy. The use of DFT-MD to calculate IR-PD spectra at low and elevated temperatures was found remarkably accurate and useful in precise structural characterization. The dynamical spectra have in particular provided the opportunity to estimate the clusters temperatures in the IR-PD experiments. The temperatures for Li(+)(H2O)(3-4)Ar are estimated at 50-60 K whereas Li(+)(H2O)3 and Li(+)(H2O)4 have been estimated at around 500-600 and 400 K, respectively.

High energy conformers of M(+)(APE)(H2O)(0-1)Ar(0-1) clusters revealed by combined IR-PD and DFT-MD anharmonic vibrational spectroscopy.

IR-PD vibrational spectroscopy and DFT-based molecular dynamics simulations are combined in order to unravel the structures of M(+)(APE)(H2O)0-1 ionic clusters (M = Na, K), where APE (2-amino-1-phenyl ethanol) is commonly used as an analogue for the noradrenaline neurotransmitter. The strength of the synergy between experiments and simulations presented here is that DFT-MD provides anharmonic vibrational spectra that unambiguously help assign the ionic clusters structures. Depending on the interacting cation, we have found that the lowest energy conformers of K(+)(APE)(H2O)0-1 clusters are formed, while the lowest energy conformers of Na(+)(APE)(H2O)0-1 clusters can only be observed through water loss channel (i.e. without argon tagged to the clusters). Trapping of higher energy conformers is observed when the argon loss channel is recorded in the experiment. This has been rationalized by transition state energies. The dynamical anharmonic vibrational spectra unambiguously provide the prominent OH stretch due to the OH···NH2 H-bond, within 10 cm(-1) of the experiment, hence reproducing the 240-300 cm(-1) red-shift (depending on the interacting cation) from bare neutral APE. When this H-bond is not present, the dynamical anharmonic spectra provide the water O-H stretches as well as the rotational motion of the water molecule at finite temperature, as observed in the experiment.

Theoretical investigations on CaO ions: vibronic states and photoelectron spectroscopy.

The low-lying electronic states, X(2)Π and A(2)Σ(+) of CaO(+) and X(2)Σ(+) and A(2)Π of CaO(-), have been determined at the MRCI+Q level of theory with the aug-cc-pV5Z(O) and cc-pCV5Z(Ca) basis sets. The two states of CaO(+) are close within <0.1 eV and coupled via spin-orbit effect. The X(2)Σ(+) and A(2)Π states of CaO(-) are energetically separated by <1 eV such that the first excited state is close to the electronic ground state of neutral CaO and unstable with respect to electron detachment. Using the potential energy curves and the spin-orbit coupling terms, the vibronic energy levels of these ions have been determined. The ionization energy and the electron affinity of CaO are calculated at 6.79 and 0.79 eV, respectively. The photoelectron spectra of CaO(-) and CaO have also been simulated.

Metastable ClO2+ and ClO3+ ions in the gas phase: a combined theoretical and mass spectrometric investigation.

We have performed a detailed theoretical study applying large ab initio computations of the low lying electronic states of ClO(2+) and ClO(3+) and an experimental search for these ClO(2+) and ClO(3+) gas-phase species. For both species, we have found electronic states with potential barriers with respect to dissociation, where these multiply positively charged diatomic ions can exist in the gas phase as long-lived metastable molecules. Our potential energy curves are used to predict the double-ionization spectrum of ClO and to derive a set of spectroscopic parameters for the metastable bound states of these species. At the MRCI + Q/aug-cc-pV5Z level, the adiabatic double and triple ionization energies of ClO are computed to be 32.4 eV and 65.0 eV, respectively. Experimentally, we confirm the existence of ClO(2+) using mass spectrometry. ClO(2+) could be produced by energetic, high-current oxygen ((16)O(-)) ion beam sputtering of PdCl(2) and NH(4)Cl powders and survived a flight time of ~9 µs. We report also the experimental observation of the ClN(2+), PdCl(2+) and InO(2+) diatomic doubly charged ions.

Oxygen-containing gas-phase diatomic trications and tetracations: ReO(z+), NbO(z+) and HfO(z+) (z=3, 4).

Three oxygen-containing gas-phase diatomic trications ReO(3+), NbO(3+) and HfO(3+) as well as the diatomic tetracation NbO(4+) have been observed by mass spectrometry at non-integer m/z values. These unusual triply charged molecular ion species, together with the corresponding diatomic dications ReO(2+), NbO(2+) and HfO(2+), were produced by energetic, high-current oxygen ((16)O(-)) ion beam sputtering of rhenium, niobium and hafnium metal samples, respectively, whose surfaces were dynamically oxidized by oxygen primary ion incorporation. In addition, NbO(z+) (z≤ 4) were generated by intense femtosecond laser excitation and photofragmentation (Coulomb explosion) of Nb(x)O(y) clusters and were detected through Time-of-Flight Mass Spectrometry (TOF). Our experimental results confirm previous reports on the detection of NbO(4+), NbO(3+), NbO(2+), HfO(3+) and HfO(2+) with Atom Probe mass spectrometry, whereas ReO(3+) and ReO(2+) apparently had not been observed before. In addition, these multiply charged molecular ions have been studied theoretically for the first time. Ab initio calculations of their electronic structures show that the diatomic trications ReO(3+), NbO(3+) and HfO(3+) are long-lived metastable gas-phase species, with bond lengths of 1.61 Å, 1.62 Å and 1.86 Å, respectively. They present large potential barriers with respect to dissociation of more than 2.7 eV. The corresponding diatomic dications are thermochemically stable molecules with very large dissociation energies (>3.5 eV). Our calculations predict the diatomic tetracation ReO(4+) to be a metastable ion species in the gas phase. We compute a potential barrier toward fragmentation of 0.6 eV; its formation requires a quadruple adiabatic ionization energy of 85.7 eV. Even though our calculations show that NbO(4+) is a weakly bound (dissociation barrier ∼0.1 eV) metastable molecule, it is here identified via linear time-of-flight mass spectrometry.

Mg2H2: new insight on the Mg-Mg bonding and spectroscopic study.

The six dimensional potential energy surface of the electronic ground state X̃(1)Σ(g)(+) of Mg(2)H(2) has been generated by the coupled-cluster approach with single, double and perturbative triple excitations [CCSD(T)] combined with the aug-cc-pCVTZ basis set for Mg atoms and the aug-cc-pVTZ basis set for the H atoms. The analytical representation of this surface was used in variational calculations of the rovibrational energies of Mg(2)H(2), Mg(2)D(2), and HMg(2)D for J = 0 and 1. For Mg(2)H(2), the rotational constant B(0) is computed to be 0.1438 cm(-1), and the fundamental anharmonic wavenumbers are calculated to be ν(1) = 1527.3 cm(-1) (Σ(g)(+)), ν(2) = 275.3 cm(-1) (Σ(g)(+)), ν(3) = 1503.6 cm(-1) (Σ(u)(+)), ν(4) = 312.9 cm(-1) (Π(g)), and ν(5) = 256.5 cm(-1) (Π(u)). In addition, the electronic ground states of Mg(2)H, MgH(2), Mg(2), and MgH have been investigated in order to compute the bonding energies of Mg(2)H(2) and to explain the strength of the Mg-Mg bond in this tetra-atomic molecule. The nature of the low-lying excited states of Mg(2)H(2) is also studied.

Titan's ionic species: theoretical treatment of N2H+ and related ions.

We use different ab initio methods to compute the three-dimensional potential energy surface (3D-PES) of the ground state of N(2)H(+). This includes the standard coupled cluster, the complete active space self-consistent field, the internally contacted multi reference configuration interaction, and the newly developed CCSD(T)-F12 methods. For the description of H and N atoms, several basis sets are tested. Then, we incorporate the 3D-PES analytical representations into variational calculations of the rovibrational spectrum of N(2)H(+)(X(1)Sigma(+)) up to 7200 cm(-1) above the zero point vibrational energy. Our data show that the CCSD(T)-F12/aug-cc-pVTZ approach represents a compromise for good description of the PES and computation cost. This technique is recommended for full dimensional PES generation of atmospheric and astrophysical relevant polyatomic systems. We applied this method to derive the rovibrational spectra of N(2)H(+)(X(1)Sigma(+)) and of N(2)H(++)(X(2)Sigma(+)). Finally, we discuss the existence of the N(2)H(++)(X(2)Sigma(+)) in Titan's atmosphere.

Ionic chemistry of tetravinylsilane cation (TVS+) formed by electron impact: theory and experiment.

We performed experimental and ab initio studies on tetravinylsilane cation (TVS(+)) and its ionic and neutral fragmentation products. The aim of the study is the assignment of the products formed in electron impact ionization reaction of TVS. The experimental data were compared with ab initio data calculated at the MP2/cc-pVDZ level of theory. We found good agreement between the calculated reaction enthalpies and experimental appearance energies of the ions. More generally, our calculations reveal that there is a competition between intramolecular isomerization and fragmentation processes occurring after ionization of TVS, leading to the formation of a multitude of neutral and ionic species important for characterizing the silicon-carbon-containing plasma and media. New routes for the synthesis of bearing silicon molecules are suggested.

Spectroscopy, metastability, and single and double ionization of AlCl.

Large calculations are done to investigate the valence and inner-valence electronic states of aluminum monochloride and its cationic species AlCl+ and AlCl2+, allowing their definite assignment. This concerns particularly the computations of the potential-energy curves of the electronic states of these species and their spin-orbit couplings and transition moments. An accurate set of spectroscopic constants for these species is also deduced. For the neutral molecule, our calculations show that the lifetimes of the AlCl A1pi v' > or = 10 levels are reduced to the 0.1-0.01 ps time scale because of spin-orbit induced predissociation processes and by tunneling through the potential barrier of the A state. Our potential curves for the ground state of AlCl and those of the cationic and dicationic species are also used for predicting the single and double ionization spectrum of AlCl. For both the cation and the dication, long-lived rovibrational levels are predicted.

Microscopic agglutination test on captive rattlesnakes : Data on serovars and titers.

The microscopic agglutination test (MAT) is considered the "golden standard" leptospirosis serodiagnostic test, but there is little information about it as it pertains to snakes. To fill this information gap, we provide data on serovars and titers of fifty-six Crotalus durissus collilineatus sera samples that tested positive by MAT (10.1016/j.actatropica.2016.02.006 (Rodrigues et al., 2016) [5]). These data are presented in a table, along with a description of the methodology used for sample collection and serologic testing.

Anti-Leptospira spp. antibodies in Crotalus durissus collilineatus kept in captivity and its zoonotic relevance.

Leptospirosis is a worldwide spread zoonosis that can affect all groups of vertebrates, including reptiles. Because it has been little studied in snakes, this study focused on determining the occurrence of anti-Leptospira spp. antibodies in 64 Crotalus durissus collilineatus kept in captivity and on identifying the most common serovars in these animals, using the microscopic agglutination test. Of these, almost 90% were positive and there were reactions to the 22 serovars used in the study. The most common serovar in these snakes was Javanica, Andamana and Patoc. Most frequent titers were 25 and 50, although high titers (such as 1600) were also recorded, despite the absence of clinical symptoms. The possibility should be considered of captive snakes serving as a serious source of leptospiral infection in humans, which is why it is essential to study, prevent and control the disease in breeding centers and serpentariums.