Dipole Moment Vector Research Articles

Exploring (NH2F)2, H2FP:NFH2, and (PH2F)2Potential Surfaces: Hydrogen Bonds or Pnicogen Bonds?

An ab initio MP2/aug'-cc-pVTZ study has been carried out to identify local minima on the (NH(2)F)(2), H(2)FP:NFH(2), and (PH(2)F)(2) potential surfaces, to characterize the types of interactions which stabilize the complexes found at these minima, and to evaluate their binding energies. With one exception, (NH(2)F)(2) complexes are stabilized by N-H···N or N-H···F hydrogen bonds. Only one complex, that with the smallest binding energy, has a pnicogen N···N bond. In contrast, (PH(2)F)(2) complexes are stabilized by P···P or P···F pnicogen bonds or by an antiparallel alignment of the dipole moment vectors of the two monomers, but not by hydrogen bonds. The most stable complex has an F-P···P-F alignment which approaches linearity. Both hydrogen-bonded and pnicogen-bonded complexes exist on the H(2)FP:NFH(2) surface, with the most stable being the pnicogen-bonded complex with F-P···N-F approaching a linear arrangement. Charge transfer transitions from a lone pair on a P, N, or F atom in one molecule to an antibonding σ* orbital of the other stabilize these complexes. These transitions are most important for complexes with pnicogen bonds. Although net charge transfer occurs in complexes in which the two monomers are inequivalent, charges on N and P do not correlate with N and P absolute chemical shieldings. Rather, these shieldings also reflect charge distributions and overall bonding patterns. EOM-CCSD two-bond spin-spin coupling constants (2h)J(X-Y) across X-H···Y hydrogen bonds tend to be small, due in part to the nonlinearity of many of the hydrogen bonds. (1p)J values across a particular kind of pnicogen bond are relatively large and vary significantly but do not correlate with corresponding distances.

Surface Susceptibility Bianisotropic Matrix Model for Periodic Metasurfaces of Uniaxially Mono-Anisotropic Scatterers Under Oblique TE-Wave Incidence

A bianisotropic matrix technique is presented for the development of a homogenized surface susceptibility model of metasurfaces with arbitrary uniaxially mono-anisotropic scatterers, illuminated by obliquely incident TE waves. Based on the sole assumption that the scatterers can be described by point-dipoles, the proposed formulation establishes a simple relation between the homogenized metasurface susceptibility matrix and the scatterer polarizability matrix. For this purpose, the exact interaction coefficients, associating the metasurface local field vectors with the dipole moment vectors, are extracted in terms of rapidly convergent series. The resulting analytical expressions for the interaction coefficients are applicable to both near- and far-field problems. Moreover, the derived formula for the surface susceptibility matrix reveals the existence of off-diagonal terms, corresponding to a magnetoelectric coupling effect at the lattice level. The accuracy of the method is verified via comparisons with full-wave-simulation results for several metasurfaces of planar resonators and magnetodielectric spheres. It is observed that the efficiency of the model is contingent upon the electrical size of the scatterers rather than the lattice periodicity, since the former determines the validity of the point-dipole approximation, which is the only assumption throughout the analysis.

Synthesis and Molecular Properties of Acceptor‐Substituted Squaraine Dyes

A broad series of more than 20 acceptor-substituted squaraines was synthesized that feature different acceptor functionalities at the central squaraine four-membered ring. The influence of these acceptor units on the reactivity of semisquaraine precursors and stability of the respective squaraines were explored. Thereby the dicyanovinyl group was found to be the most versatile acceptor group that enabled various modifications at the donor moiety of the squaraine scaffold, leading to an extended series of dicyanovinyl-functionalized squaraines. The variation of donor units afforded a set of NIR fluorophores that cover a wavelength region from the visible at about 650 nm far into the NIR up to 920 nm with fluorescence quantum yields between 0.93 and 0.11 and outstanding optical brightness. This excellent optical property is related to a rigid molecular scaffold that is fixed in an all-cis configuration by the additional dicyanovinyl acceptor unit. The change of the molecular symmetry from C(2h) to C(2v) upon functionalization of the squaraine core with dicyanovinyl acceptor group has been confirmed in solution by electro-optical absorption (EOA) spectroscopy, revealing permanent ground-state dipole moments μ(g) in the range between 4.3 and 6.4 D. These dipole moments direct an antiparallel packing of the molecules in the solid state according to single-crystal X-ray analyses achieved for four dicyanovinyl-functionalized squaraines. The structural properties, the EOA results, as well as the band shapes of the optical spectra indicate that these polymethine dyes are cyanine-type chromophores. It is worth noting that the orientation of the dipole moment vectors is orthogonal to the orientation of the transition dipole moment vectors, which is an uncommon but characteristic feature of this rather novel class of polymethine dyes. With regard to applications of these dyes in organic solar cells, their redox properties were also studied by cyclic voltammetry.

Enhancement of Twist Angle Dependent Two-Photon Activity through the Proper Alignment of Ground to Excited State and Excited State Dipole Moment Vectors

Herein, we show that the two-photon (TP) transition probability (δTP) of o-betaine system will reach its maximum value at a twist angle around 65°. However, the potential energy scan with respect to the twist angle between its two rings indicates that the molecule in its ground state is quite unstable at this twist angle. Out of the different possibilities, the one having a single methyl group at the ortho position of the pyridinium ring is found to attain the optimum twist angle between the two rings, and interestingly, this particular substituted o-betaine has larger δTP value than any other substituted or pristine o-betaine. The twist angle dependent variation of δTP has been explained by employing the generalized-few-state-model formula for 3D molecules. The results clearly reveal that the magnitude of ground to excited state and excited state dipole moment vectors as well as the angle between them are strongly in favor of maximizing the overall δTP values at the optimum twist angle. The constructive interference between the optical channels at the optimum twist angle also plays an important role to achieve the maximum δTP value. Furthermore, to give proper judgment on our findings, we have also performed solvent phase calculations on all the model systems in nonpolar solvents, namely, cyclohexane and n-hexane, and the results are quite consistent with the gas phase findings. The present study will definitely offer a new way to synthesize novel two-photon active material based on o-betaine.

Theoretical and Experimental Studies on Circular Dichroism of Carbo[n]helicenes

The chiroptical properties of a series of carbo[n]helicenes (n = 4-10) were investigated by the state-of-the-art approximate coupled cluster and density functional theory calculations. The theoretical calculation at the RI-CC2/TZVPP//DFT-D2-B97-D/TZVP level nicely reproduced the experimental CD spectra in both excitation energy and rotational strength without any shift or scaling. These calculations afforded the electric and the magnetic transition dipole moment vectors in [n]helicenes, allowing us to discuss the observed rotational strengths as a function of the number of benzene rings. Although the observed CD intensity was not immediately correlated to any of the calculated parameters, the anisotropy (g) factor of the (1)B(b) band and the specific rotation were found inversely proportional to n and nicely correlated with the helical pitch, but discontinuous at n = 6, where the aromatic rings start to overlap. In contrast, the g factor at the (1)B(a) band was rather insensitive to n. It was also revealed that the excitation energies of the (1)B(b) and (1)B(a) bands are inversely proportional to n over the entire range of n examined. The theoretical predictions also enabled us to rectify the erroneous experimental CD spectra of [5]- and [6]helicenes reported earlier, by using the enantiopure samples resolved by chiral HPLC.

Investigation of the polarization dependent attenuated total reflection infrared spectra of ordered lipids assisted by principal component analysis

The information about molecular architecture of oriented lipid multibilayers stacks is frequently extracted from linearly polarized infrared spectra. Usually, the measurements are limited only to the parallel and perpendicular direction of the vector of the electric field relative to the plane of incidence. The absorbance differences are measured by linear dichroism, defined as the change in absorbance that occurs when the electric vector of the radiation beam is rotated by 90°. On a basis of the dichroism value, the so-called infrared order parameter that depends on the orientation of the transition dipole moment vector with respect to the surface normal can be determined. In the studies reported here, the measurements have been carried out at angles of the electric field changing with the step of 5° in a range between the parallel and perpendicular direction. The polarization-dependent spectra were pretreated by a procedure to eliminate from the total absorbance the component shaped solely by the specific dependence of the ATR absorbance on the effective penetration depth. The principal component analysis (PCA) done for the standard normal variate (SNV) pretreated spectra has shown that the obtained model based on one component is able to describe spectral variability with a reproducibility better than 95%. Lack of any other phenomenon that modulates the analysed spectral variations is undeniable proof that the raw data were well “cleaned” from the unwanted effect. The loading value for a given variable strictly correlates with orientation of the transition dipole moment vector for the corresponding mode with respect to the surface normal. PCA results obtained for the polarization-dependent spectra of the dry lipid film measured as function of temperature give information about the contribution of different parts of the DPPC molecule in the melting of the lipid film within the gel phase.

Iterative diagonalization in the state-averaged multi-configurational time-dependent Hartree approach: Excited state tunneling splittings in malonaldehyde

An iterative block Lanczos-type diagonalization scheme utilizing the state-averaged multi-configurational time-dependent Hartree (MCTDH) approach is introduced. Combining propagation in real and imaginary time and using a set of initial seed wavefunctions corresponding to excitations via the different components of the dipole moment vector, the scheme can favorably be used to selectively compute vibrational states which show high intensities in vibrational absorption spectra. Tunneling splitted vibrational states in double well systems can be described particularly efficient employing an increased set of seed wavefunctions which includes symmetric and anti-symmetric wavefunctions simultaneously. The new approach is used to study the tunneling splittings of the vibrationally excited states of malonaldehyde. Full-dimensional multi-layer MCTDH calculations are performed and results for the tunneling splittings of several excited vibrational states can be obtained. The calculated tunneling splittings agree reasonably well with available experimental data. Order of magnitude differences between tunneling splittings of different vibrationally excited states are found and interpreted.

Molecular and Electronic Structure, Magnetotropicity and Absorption Spectra of Benzene–Trinuclear Copper(I) and Silver(I) Trihalide Columnar Binary Stacks

The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 Å at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 Å) and Ag···C (3.44 Å). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems.

Resolving the contribution due to Förster-type intramolecular electronic energy transfer in closely coupled molecular dyads

This work examines the electronic energy-transfer (EET) processes inherent to a molecular dyad in which aryl polycycles attached to a boron dipyrromethene (Bodipy) dye act as ancillary light harvesters for near-UV photons. The solvent, being methyltetrahydrofuran, is compressed under applied pressure to such an extent that, over the accessible pressure range, there is a 25% decrease in molar volume. This effect serves to increase the effective concentration of the solute and increases fluorescence from Bodipy when this chromophore is excited directly. Illumination into the aryl polycycles, namely pyrene and perylene derivatives, leads to rapid intramolecular EET to Bodipy but fluorescence from these units is partially restored under high pressure. The argument is made that applied pressure restricts torsional motions around the linkages and imposes a near orthogonal geometry for transition dipole moment vectors on the reactants. In turn, this pressure-induced conformational restriction switches off Forster-type EET within the system, leaving the electron-exchange contribution. For the target dyad, the Forster component is ca. 5% for pyrene and ca. 25% for perylene. Such contributions are not inconsistent with calculations made on the basis of Forster theory but modelling is rendered difficult by the absence of accurate information about the nature of the conformational motion. Two possibilities have been considered. In the first case, the appendages remain stiff but pressure reduces the extent of displacement from the lowest-energy position. The results can be accounted for in a quantitative sense on the basis of small deviations from the lowest-energy conformation; the actual amount of displacement needed to explain the pressure effect depends on the method used to compute the Forster rates and ranges from ca. 4° for the ideal dipole approximation to only 0.5° for the extended dipole method. Secondly, pressure is assumed to bend each appendage into a banana-like shape. Again, the full effect of applied pressure can be accounted for by way of minor curvature of the linkage.

Quantum investigation of non-bonded interaction between the B15N15 ring and BH2NBH2 (radical, cation, anion) systems: a nano molecularmotor

The electromagnetic non-bonded interactions of BH2NBH2 molecule inside the B15N15 ring has been investigated with B3LYP method using EPR-II and EPR-III basis sets. Optimized structures, relative stability, and hyperfine spectroscopic parameters, such as total atomic charges, spin densities, electrical potential, and isotropic Fermi coupling constants of radical, cationic, and anionic forms of BH2NBH2 in different loops and bonds have been calculated. The spectral properties have been contributed to explain the characteristics of hyperfine electronic structure. The calculation for the B15N15–BH2NBH2 system and then for adenine–thymine base pairs coupled with BH2NBH2 molecule inside the B15N15 ring (A–BNB–T) have been done and three quantized rotational frequencies for transitions among cationic, radical, and anionic have been calculated, too. All observed frequencies appeared in the IR rotational region. So, this system can be used for the measurement of rotational spectra related to electrical voltage differences existing in macromolecules such as proteins and DNA and membrane. Extensive calculations have been carried out on the radical, anionic, and cationic forms of BH2NBH2 to obtain data and it has been observed that the radial coordinate of the dipole moment vector (r) as well as the voltage differences (ΔV) and relative energies (ΔE) exhibited Gaussian distribution. We have obtained a relationship between dipole moments and the voltage differences and energies of system.

Molecular Dynamics Study of Water Interacting with Siloxane Surface Modified by Poly(ethylene oxide) Chains

In this work, static and dynamic properties of interfacial water molecules on the amorphous siloxane surface covered by poly(ethylene oxide) (PEO) chains grafted at different coverage densities σ were studied using atomistic molecular dynamics simulations. It is shown that water molecules compete with the ethylene oxide (EO) monomers for interaction sites on the siloxane surface and for the space above it. Two types of orientations of the water molecules are identified as the most populated: one with the dipole moment vector pointing toward the siloxane surface and another with the dipole moment vector pointing about 5° away from the surface. In both the hydrogen pair is amenable to rotate around the dipolar axis. The higher the coverage density the larger the disorder of water molecules, but the dipole moment-down orientation still dominates. The number of water–water hydrogen bonds monotonically decreases with σ, whereas the number of water–PEO hydrogen bonds displays a maximum around the crossover to t...

Ab initio DFT study of bisphosphonate derivatives as a drug for inhibition of cancer: NMR and NQR parameters

DFT computations were carried out to characterize the (17)Oand (2)H electric field gradient, EFG, in various bisphosphonate derivatives. The computations were performed at the B3LYP level with 6-311++G (d,P) standard basis set. Calculated EFG tensors were used to determine the (17)O and (2)H nuclear quadrupole coupling constant, χ and asymmetry parameter, η. For better understanding of the bonding and electronic structure of bisphosphonates, isotropic and anisotropic NMR chemical shieldings were calculated for the (13)C, (17)O and (31)P nuclei using GIAO method for the optimized structure of intermediate bisphosphonates at B3LYP level of theory using 6-311++G (d, p) basis set. The results showed that various substituents have a strong effect on the nuclear quadrupole resonance (NQR) parameters (χ, η) of (17)O in contrast with (2)H NQR parameters. The NMR and NQR parameters were studied in order to find the correlation between electronic structure and the activity of the desired bisphosphonates. In addition, the effect of substitutions on the bisphosphonates polarity was investigated. Molecular polarity was determined via the DFT calculated dipole moment vectors and the results showed that substitution of bromine atom on the ring would increase the activity of bisphosphonates.

Three-dimensional localization of neurons in cortical tetrode recordings

The recording radius and spatial selectivity of an extracellular probe are important for interpreting neurophysiological recordings but are rarely measured. Moreover, an analysis of the recording biophysics of multisite probes (e.g., tetrodes) can provide for source characterization and localization of spiking single units, but this capability has remained largely unexploited. Here we address both issues quantitatively. Advancing a tetrode (≈40-μm contact separation, tetrahedral geometry) in 5- to 10-μm steps, we repeatedly recorded extracellular action potentials (EAPs) of single neurons in the visual cortex. Using measured spatial variation of EAPs, the tetrodes' measured geometry, and a volume conductor model of the cortical tissue, we solved the inverse problem of estimating the location and the size of the equivalent dipole model of the spike generator associated with each neuron. Half of the 61 visual neurons were localized within a radius of ≈100 μm and 95% within ≈130 μm around the tetrode tip (i.e., a large fraction was much further than previously thought). Because of the combined angular sensitivity of the tetrode's leads, location uncertainty was less than one-half the cell's distance. We quantified the spatial dependence of the probability of cell isolation, the isolated fraction, and the dependence of the recording radius on probe size and equivalent dipole size. We also reconstructed the spatial configuration of sets of simultaneously recorded neurons to demonstrate the potential use of 3D dipole localization for functional anatomy. Finally, we found that the dipole moment vector, surprisingly, tended to point toward the probe, leading to the interpretation that the equivalent dipole represents a "local lobe" of the dendritic arbor.

Theoretical study on the electronic, structural, properties and reactivity of a series of mono-, di-, tri- and tetrachlorothiophenes as well as corresponding radical cation forms as monomers for conducting polymers.

In this paper, electrical and structural properties of mono-, di-, tri- and tetrachlorothiophenes and their radical cations have been studied using the density functional theory and B3LYP method with 6-311++G** basis set. The effects of the number and position of the substituent of chlorine atoms on the properties of the thiophene ring for all chlorothiophenes and their radical cations have been studied. Vibrational frequencies, nuclear chemical shielding constants, spin-density distribution, size and direction of dipole moment vector, ionization potential, electric polarizabilities and NICS values of these compounds have been calculated as well. The analysis of these data showed that double bonds in 3-chlorothiophene are more delocalized and it is the best possible candidate monomer among all chlorothiophenes for the synthesis of corresponding conducting polymers with modified characteristics.

Theoretical study on the electronic, structural, properties and reactivity of a series of mono-, di-, tri- and tetrafluorothiophenes as monomers for new conducting polymers

Electrical and structural properties of mono-, di-, tri- and tetrafluorothiophenes and their radical cations have been studied using density functional theory and B3LYP method with 6-311++G** basis set. The effects of the number and position of the substituent of fluorine atoms on the properties of the thiophene ring have been studied using optimized structures obtained for these molecules and their radical cations. Vibrational frequencies, spin-density distribution, size and direction of dipole moment vector, ionization potential, electric polarizability, HOMO–LUMO gaps and NICS values of these compounds have been calculated as well. The analysis of these data showed that double bonds in 3-fluorothiophene are more delocalized and it is the best possible candidate monomer among all fluorothiophenes for the synthesis of corresponding conducting polymers with modified characteristics.

On the origin dependence of the angle made by the electric and magnetic vibrational transition dipole moment vectors

The concept of robustness of rotational strengths of vibrational modes in a VCD spectrum has been introduced as an aid in assignment of the absolute configuration with the help of the VCD spectrum. The criteria for robustness have been based on the distribution around 90° of the angles ξ(i) between electric and magnetic transition dipoles of all the modes i of a molecule. The angles ξ(i) (not, of course, the rotational strengths) are, however, dependent on the choice of origin. The derived criteria are for the center of mass chosen as the origin of the coordinate system. We stress in this note that application of the derived criteria assumes that excessive translation of the coordinate origin is not applied. Although the ξ(i) angles are not very sensitive to the position of the origin, very small displacements (a few Å) are not a problem, excessive translation of the origin does have considerable effect on the ξ(i) angles. In this note we quantify this effect and demonstrate how the distribution of ξ(i) angles is affected. Although it is possible to recalibrate the robustness criteria for the angles for a specific (large) displacement, we recommend that such displacement simply be avoided. It is to be noted that some modeling software does yield output with excessively displaced coordinate origin; this should be checked and corrected.

Generalized stern models of the electric double layer considering the spatial variation of permittvity and finite size of ions in saturation regime.

The interaction between a charged metal implant surface and a surrounding body fluid (electrolyte solution) leads to ion redistribution and thus to formation of an electrical double layer (EDL). The physical properties of the EDL contribute essentially to the formation of the complex implant-biosystem interface. Study of the EDL began in 1879 by Hermann von Helmholtz and still today remains a scientific challenge. The present mini review is focused on introducing the generalized Stern theory of an EDL, which takes into account the orientational ordering of water molecules. To ascertain the plausibility of the generalized Stern models described, we follow the classical model of Stern and introduce two Langevin models for spatial variation of the relative permittivity for point-like and finite sized ions. We attempt to uncover the subtle interplay between water ordering and finite sized ions and their impact on the electric potential near the charged implant surface. Two complementary effects appear to account for the spatial dependency of the relative permittivity near the charged implant surface — the dipole moment vectors of water molecules are predominantly oriented towards the surface and water molecules are depleted due to the accumulation of counterions. At the end the expressions for relative permittivity in both Langevin models were generalized by also taking into account the cavity and reaction field.

The electronic structure and dipole moment of charybdotoxin, a scorpion venom peptide with K + channel blocking activity

The electronic structure of charybdotoxin (ChTX), a scorpion venom peptide that is known to act as a potassium channel blocker, is investigated with the aid of semiempirical molecular orbital (MO) calculations. The dipole moment vector ( μ = 145 D at pH = 3.5 and μ = 116 D at pH = 7.5) of ChTX can be steered by the KcsA potassium channel’s macrodipole thereby assuming the proper orientation before the peptide binds the ion channel on the cell surface. The localization of the frontier orbitals of ChTX has been revealed for the first time. HOMO is localized on Trp14 while the three lowest-unoccupied MOs (LUMO, LUMO + 1, and LUMO + 2) are localized on the three disulfide bonds that characterize this peptide. An effective approach to engineer the HOMO–LUMO (H–L) gap of ChTX is replacing its Trp14 residue with Ala14 whereas deletion of the LUMO-associated disulfide bond Cys13-Cys33 through the insertion of a pair of l-α-aminobutyric acid residues does not affect the H–L energy gap. Molecular electrostatic potential surfaces for three ChTX models, two of them charged and one neutral, are in good agreement with the direction of the corresponding electric dipole moments.

The infrared spectrum of cyclic-N3: Theoretical prediction

We have carried out the first calculations of the infrared absorption spectrum of cyclic-N(3). Accurate vibrational energies and wave functions computed with incorporation of the geometric phase effect (via gauge theory) and using an ab initio potential energy surface were employed in this work. A sophisticated fully dimensional dipole moment function was constructed using accurate ab initio calculations and a three-dimensional-spline interpolation. Transformation of the dipole moment vector function from the reference frame associated with instantaneous principal axes of inertia to the laboratory-fixed reference frame was carried out using hyperspherical coordinates. We found that the permanent dipole moment of cyclic-N(3) in the ground vibrational state is relatively small (170 mD). The excited vibrational states show permanent dipole moments in the 10-25 mD range. The most intense part of the infrared absorption spectrum is observed in the deep infrared part of spectrum, 75-275 cm(-1), where five lines exhibit absolute absorption intensities in the range between 0.5 and 1.2 km/mol. These transitions correspond to excitation of the pseudorotational progression of states. Several unique spectroscopic features discussed in the paper should help to identify cyclic-N(3) in the laboratory.

SIMULATIONS OF WINDS OF WEAK-LINED T TAURI STARS. II. THE EFFECTS OF A TILTED MAGNETOSPHERE AND PLANETARY INTERACTIONS

Based on our previous work (Vidotto et al. 2009a), we investigate the effects on the wind and magnetospheric structures of weak-lined T Tauri stars due to a misalignment between the axis of rotation of the star and its magnetic dipole moment vector. In such configuration, the system loses the axisymmetry presented in the aligned case, requiring a fully 3D approach. We perform 3D numerical MHD simulations of stellar winds and study the effects caused by different model parameters. The system reaches a periodic behavior with the same rotational period of the star. We show that the magnetic field lines present an oscillatory pattern and that by increasing the misalignment angle, the wind velocity increases. Our wind models allow us to study the interaction of a magnetized wind with a magnetized extra-solar planet. Such interaction gives rise to reconnection, generating electrons that propagate along the planet's magnetic field lines and produce electron cyclotron radiation at radio wavelengths. We find that a close-in Jupiter-like planet orbiting at 0.05AU presents a radio power that is ~5 orders of magnitude larger than the one observed in Jupiter, which suggests that the stellar wind from a young star has the potential to generate strong planetary radio emission that could be detected in the near future with LOFAR. This radio power varies according to the phase of rotation of the star. We also analyze whether winds from misaligned stellar magnetospheres could cause a significant effect on planetary migration. Compared to the aligned case, we show that the time-scale tau_w for an appreciable radial motion of the planet is shorter for larger misalignment angles. While for the aligned case tau_w~100Myr, for a stellar magnetosphere tilted by 30deg, tau_w ranges from ~40 to 70Myr for a planet located at a radius of 0.05AU. (Abridged)