ICl Molecules Research Articles

Facile heterolytic bond splitting of molecular chlorine upon reactions with Lewis bases: Comparison with ICl and I2.

Formation of molecular complexes and subsequent heterolytic halogen-halogen bond splitting upon reactions of molecular Cl2 with nitrogen-containing Lewis bases (LB) are computationally studied at M06-2X/def2-TZVPD and for selected compounds at CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz levels of theory. Obtained results are compared with data for ICl and I2 molecules. Reaction pathways indicate, that in case of Cl2∙LB complexes the activation energies for the heterolytic Cl-Cl bond splitting are lower than the activation energies of the homolytic splitting of Cl2 molecule into chlorine radicals. The heterolytic halogen splitting of molecular complexes of X2∙Py with formation of [XPy2]+… contact ion pairs in the gas phase is slightly endothermic in case of Cl2 and I2, but slightly exothermic in the case of ICl. Formation of {[ClPy2]+… }2 dimers makes the overall process exothermic. Taking into account that polar solvents favor ionic species, generation of donor-stabilized Cl+ in the presence of the Lewis bases is expected to be favorable. Thus, in polar solvents the oxidation pathway via donor-stabilized Cl+ species is viable alternative to the homolytic Cl-Cl bond breaking.

Thermomagnetic Models for the Improved Rosen–Morse Oscillator

ABSTRACTThis study solves the radial Schrödinger wave equation (RSWE) with the improved Rosen–Morse (IRM) potential constrained by an electromagnetic field. Energy eigenvalues are derived using the parametric Nikiforov–Uvarov method and Pekeris approximation. The internal partition function, isobaric molar heat capacity formula, and magnetization model are then deduced from the equation governing pure vibrational energy states. These analytical models are applied to several pure substances, specifically Br2 (X 1Σg+), BrF (X 1Σ+), ICl (X 1Σg+), and P2 (X 1Σg+) molecules. Numerical approximations of the energy eigenvalues for these molecules closely match their exact values. The isobaric molar heat capacity expression yields mean percentage absolute deviations of 1.6585%, 0.9162%, 1.2193%, and 0.7232% when compared against experimental data for Br2 (X 1Σg+), BrF (X 1Σ+), ICl (X 1Σg+), and P2 (X 1Σg+), respectively. These results align well with other heat capacity models in existing literature.

Improved q-deformed Scarf II oscillator

In this work, the improved q-deformed Scarf II oscillator (IQSO) is formulated through the Varshni conditions for diatomic molecule potential. Equation for bound state energy eigenvalues of the IQSO is obtained by the SUSYQM method, a Pekeris-like approximation scheme is used to model the centrifugal term of the Schrödinger equation. Expressions for molar entropy and Gibbs free energy are deduced for the IQSO from equations of energy eigenvalues and partition function within the context of Poisson summation formula. The IQSO is used to model experimental Rydberg-Klein-Rees (RKR) data of six diatomic molecules including: KRb (B 1Π), CO+ (X 2Σ+), Cl2 (X 1Σg +), ICl (X 1Σg +), NbO (X 1Σ+), and K2 (X 1Σg +). The average absolute deviation and mean absolute percentage deviation are used as accuracy indicators. Computed data revealed that the IQSO is an excellent model in fitting the RKR data of the diatomic molecules examined in this work. Numerical values of molar entropy and Gibbs free energy calculated for ICl (X 1Σg +) molecule are almost indistinguishable from existing experimental data for gaseous ICl (X 1Σg +) molecules. This suggests that the IQSO is a near perfect model for representing the internal vibrations of the ICl (X 1Σg +) molecule.

Population and decay of the ArICl(ion-pair states) van der Waals complexes

The article presents the analysis of the ArICl(IP,v IP,n IP) population and decay at energies lower than the ArICl(E,vE = 0,nE ) dissociation limit (IP = E0+, , β1), v IP = 0, 1, n IP are quantum numbers of the van der Waals (vdW) modes). It shows that the ArICl(IP,v IP,n IP) lifetimes determined at spectral ranges where the ArICl(E→X, , and β→A) luminescence takes place, are the same, τ = 20.3 ± 1.0 ns, i.e. strongly mixed complex states are populated in the ArICl(IP,v IP,n IP ← A,vA,nA ) transitions, and principal channel of the complex decay is emission. We have estimated the ArICl(E0+,vE = 0) binding energy and studied the ArICl(IP,v IP,n IP) population and decay at energies higher than the ArICl(E,vE = 0,nE ) dissociation limit. Our research shows that the ArICl(IP,v IP,n IP) wave functions corresponding to specific n IP vdW mode depend on the mode, but they are approximately constant in some spectral ranges. The ArICl(IP,v IP,n IP) complex decays to free ICl(E0+,vE , and β1,vβ ) molecules. We have determined the probabilities of these decay channels and shown that all the ICl(IP) states are mixed under the action of the Ar atom, i.e. this atom does not behave in the ArICl(IP,v IP,n IP) complexes as a ‘spectator’ as it occurs in the RgI2(IP) states.

Ab Initio Study of Ion-Pair States of Halogen Molecules

The ion-pair states of IBr, ICl, and BrCl molecules correlating to the limits of dissociation X+(3P2,1,0, 1D2) + Y–(1S0) are studied using a complete active space self-consistent field (CASSCF), allowing for dynamic electronic correlations and spin–orbit interaction. Using experimental results, the calculated values of the equilibrium energy of the X+Y−(3P2) states correlating to the lowest ion state X+(3P2) are grouped in the range ΔTe ∼ 100 cm−1, with the error of their relative location also on the order of 100 cm−1. For most states, the difference between the experimental and calculated values of the equilibrium internuclear distance does not exceed $$R_{{\text{e}}}^{{\exp }}$$ – $$R_{{\text{e}}}^{{{\text{calc}}}}$$ = 0.02 A. A comparative analysis of structural features of the ion-pair states of homonuclear and heteronuclear halogen molecules is performed using results from recent ab initio calculations for the I2 molecule. We also discuss some issues concerning ion-pair states X−Y+ with inverted charge localization, which correlate to the limits of dissociation X– + Y+ and are coupled with the X+Y− states by two-electron transitions. It is noted that the structures with two stable localizations of two electrons, X+‒D‒Y− and X−‒D‒Y+, where X, Y are electron affinity centers (atoms, molecules, clusters) and D is a dielectric spacer, could be of interest for microelectronics.

Dependence of the electronic absorption spectra of aqueous solutions of iodine monochloride on the conditions of dilution and storage time

The electronic absorption spectra of aqueous solutions of iodine monochloride ICl are studied. The spectra of as-prepared solutions display the absorption band associated with hydrated ICl molecules. An additional band indicating that molecular iodine was formed in the solution emerges in the spectrum as dissolution takes place. Only the band belonging to iodine monochloride remains in the absorption spectra, and no additional bands appear after chloride anions Cl− are added to the solution. The absorption spectrum becomes more complex when ICl is dissolved in an alkaline medium. The band belonging to molecular iodine emerges in the spectra at low alkali concentrations, while being transformed to other shorter-wavelength bands at high alkali concentrations (рН ≥ 12).

Relativistic coupled cluster calculation of Mössbauer isomer shifts of iodine compounds

ABSTRACTMössbauer isomer shifts of 129I and 127I in the ICl, IBr and I2 molecules are studied. Filatov's formulation is used, based on calculating the electronic energy change of the two systems involved in the Mössbauer γ transition, the source and absorber. The energy difference between the transitions in the two systems determines the shift. The effects of relativity and electron correlation on the shifts are investigated. The exact two-component (X2C) and the four-component relativistic schemes give virtually identical results; the non-relativistic approach yields about 50% of the relativistic shifts. Electron correlation is included by coupled-cluster singles-and-doubles with perturbative triples [CCSD(T)]; it reduces Hartree–Fock shifts by 15%–20%. Basis sets are increased until the isomer shifts converge. The final results, calculated with the converged basis in the framework of the X2C Hamiltonian and CCSD(T) correlation, give an agreement of 10% or better with experimental data.

Stark effect of the hyperfine structure of ICl in its rovibronic ground state: Towards further molecular cooling**Project supported by the National Natural Science Foundation of China (Grant No. 11034002), the National Basic Research Program of China (Grant No. 2011CB921602), and Qing Lan Project, China.

Hyperfine structures of ICl in its vibronic ground state due to the nuclear spin and electric quadruple interactions are determined by diagonalizing the effective Hamiltonian matrix. Furthermore, the Stark sub-levels are precisely determined as well. The results are helpful for electro-static manipulation (trapping or further cooling) of cold ICl molecules. For example, an electric field of 1000 V/cm can trap ICl molecules less than 637 μK in the lowest hyperfine level.

Photostop of iodine atoms from electrically oriented ICl molecules**Project supported by the National Natural Science Foundation of China (Grant Nos. 11034002, 61205198, and 11274114) and the National Key Basic Research and Development Program of China (Grant No. 2011CB921602).

The dynamics of photostopping iodine atoms from electrically oriented ICl molecules was numerically studied based on their orientational probability distribution functions. Velocity distributions of the iodine atoms and their production rates were investigated for orienting electrical fields of various intensities. For the ICl precursor beams with an initial rotational temperature of ∼ 1 K, the production of the iodine atoms near zero speed will be improved by about ∼ 5 times when an orienting electrical field of ∼ 200 kV/cm is present. A production rate of ∼ 0.5‰ is obtained for photostopped iodine atoms with speeds less than 10 m/s, which are suitable for magnetic trapping. The electrical orientation of ICl precursors and magnetic trapping of photostopped iodine atoms in situ can be conveniently realized with a pair of charged ring magnets. With the maximal value of the trapping field being ∼ 0.28 T, the largest trapping speed is ∼ 7.0 m/s for the iodine atom.

Quantum Interference Effects Theoretically Found in the Photodissociation Processes of the Second Absorption Bands of ICl and IBr Molecules.

Some quantum interference effects are exposed directly in experiments, but others are not and remain just hidden and thus require thorough theoretical analysis to be exposed. In this respect, the second absorption bands of IX (X = Cl, Br) molecules show an interesting behavior in the photofragment anisotropy of the lowest I((2)P3/2)+X((2)P3/2) product channel; it changes from strongly parallel distribution on the shorter wavelength side to strongly perpendicular distribution on the longer wavelength side. Because the responsible perpendicular third Ω = 1 (1(III)) excited state correlating adiabatically to this product channel has only a weak absorption, the parallel component flux yielding the same products must be comparatively weak, even though the responsible parallel excitations to the 0(+)(III) and/or 0(+)(IV) excited states have strong absorptions. In the present theoretical study, the branching ratios and the anisotropy parameters have been obtained using the spin-orbit configuration interaction method combined with the quantum mechanical wavepacket and semiclassical approaches. Significant quantum interference effect between the two dissociative de Broglie waves on the 0(+)(III) and 0(+)(IV) potential curves has been found through the avoided crossing, and the weak parallel flux to the ground-state product channel has been explained by their destructive interference character. This interference effect has weak excitation energy dependence due to rather unique behavior of their almost parallel potential curves from the Franck-Condon to avoided crossing regions.

Photofragment translational spectroscopy of ICl near 304 and 280 nm: Observation of an intense hot band effect

The photodissociation dynamics of ICl has been studied near 304 and 280 nm on a simple miniature time of flight (mini-TOF) photofragment translational spectrometer with a short pulse of a weak acceleration field. An intense hot band effect was observed. Many small peaks were resolved in each photofragment translational spectrum (PTS). Based on simulations, the principal peaks were assigned not only to the different photodissociation channels (1) I + Cl, (2) I + Cl*, (3) I* + Cl, or (4) I* + Cl*, but also to the different chlorine isotopes (35Cl and 37Cl). Moreover, some extra peaks showed the existence of an intense hot band effect from vibrationally excited ICl molecules, though only a few percent of ICl molecules remained in the vibrationally excited states in our supersonic molecular beam. Based on the spectra near 304 nm, the quantum yield Φ of each channel, the curve crossing, and the branching fraction σ from each transition state were determined.

Ion-Pair States of I[sub 2], Br[sub 2], IBr, and ICl

The experimentally determined energies and rotational constants of the vibrational levels v = 0–20 of the Ion-Pair states Ω = 0+, Ω = 1 of the I2, Br2, IBr, and ICl molecules are modeled. The model used includes three diabatic states, which correlate to X+(3P, 1D) + Y∼(1S 0). These states are coupled by the spin-orbit interaction, which is assumed to be independent of the internuclear distance. For IBr and ICl, as well as for the ungerade states of I2 and Br2, satisfactory results are obtained. The model is less applicable to the gerade states of I2 and Br2, which is possibly results from the retainment of the asymptotic J A J B coupling of the angular momenta at equilibrium internuclear distances.

Vibrational relaxation dynamics of I35Cl(B, v′) induced by low-temperature collisions with He atoms

Using laser-induced fluorescence and two-laser, pump-probe spectroscopy, collision-induced vibrational relaxation is observed to compete with the dissociation of electronically excited ICl in a helium carrier gas expansion. By thoroughly characterizing the expansion properties, we observe that collisions of ICl(B, v'= 3) molecules with He atoms in the expansion induce vibrational relaxation of the initially prepared dihalogen down to rotor states in the next lower ICl(B,v'= 2) level on timescales that compete with the rate for non-adiabatic transfer from the B state to the Z1 state. The resulting ICl(B,v'= 2,j') product rotational distribution, along with the analogous ICl(B,v'= 1,j') distribution formed by collisional relaxation of molecules in the long-lived ICl(B,v'= 2) level are compared to ICl(B,v'= 2,j') products formed by vibrational predissociation of He...ICl complexes prepared in different intermolecular vibrational levels within the He + ICl(B,v'= 3) potential. No evidence is observed for resonance-enhanced collisional cross sections, even at the low temperatures achieved, T < 1.0 K.

Ionization and dissociation of CH2I2 and CH2ICl in femtosecond intense field

Ionization and dissociation processes of gas molecules, CH2I2 and CH2ICl, in intense femtosecond field (1013–1015 W·cm−2), were investigated by flight time mass spectrometer, irradiated by 60 fs with 800 and 400 nm femtosecond laser. In the moderate intense field, CH2I2 and CH2ICl produced concerted elimination products, I2 and ICl molecules, respectively. The multiple charged ions, I2+, generated in Coulomb explosion under intense femtosecond laser irradiation, split into three peaks in the flight time mass spectra, due to the initial kinetic energies released in the explosion. The C-I internuclear distances during Coulomb explosion and the kinetic energy released were estimated according to the flight time differences.

Dissociative ionization of ICl studied by ion imaging spectroscopy

The speed and angular distributions of I+ ions, produced when ICl molecules were exposed to both ultraviolet and visible radiation at 304+608 nm, 355+608 nm, and 304+532 nm, were measured by velocity map imaging. An intense central feature in the I+ images was observed to be very sensitive to the polarization of the ultraviolet light and is attributed to a dissociative ionization mechanism involving three-body fragmentation: ICl+hv (visible)+3hv (ultraviolet)→I++Cl+e−. The effect of varying the delay between the visible and ultraviolet radiation on the I+ images suggests that an intermediate gateway state of ICl reached by absorption of one photon of visible light mediates the transition to the superexcited dissociative ionization state.

Chemical selectivity in the remote abstractive chemisorption of ICl on Al(111).

The interaction of ICl and Al(111) involves remote dissociation in its chemisorption process. In remote dissociation, an electron harpoons from an Al(111) surface to an ICl gas molecule to initiate the chemisorption process. We have determined that ICl can chemisorb onto Al(111) by non-activated direct chemisorption, and the sticking probability of this direct channel is 0.65 +/- 0.03. Furthermore, low energy ICl molecules that do not undergo remote dissociation can chemisorb onto Al(111) by precursor-mediated chemisorption. Not only is the interaction of ICl and Al(111) reactive, it is chemically selective. Studies with Auger spectroscopy reveal that the ratio of chlorine atoms to iodine atoms on the Al(111) is 0.32 +/- 0.10 at low (0.042 +/- 0.002) surface coverage. Time-of-flight mass spectrometry studies also show that chlorine atoms are the only species scattered from the surface after ICl interacts with Al(111). These results indicate that iodine-selective abstraction, in which the iodine atom of ICl chemisorbs to the aluminium surface while the chlorine atom is ejected into the gas phase, is the dominant mechanism in this reaction. Iodine-end first collisions are more reactive than chlorine-end first collisions because the lowest unoccupied molecular orbital (LUMO) of ICl is primarily composed of iodine atomic orbitals, and it is the LUMO that interacts with the harpooning electron from the aluminium.

Aligning molecules with intense nonresonant laser fields

Molecules in a seeded supersonic beam are aligned by the interaction between an intense nonresonant linearly polarized laser field and the molecular polarizability. We demonstrate the general applicability of the scheme by aligning I2, ICl, CS2, CH3I, and C6H5I molecules. The alignment is probed by mass selective two dimensional imaging of the photofragment ions produced by femtosecond laser pulses. Calculations on the degree of alignment of I2 are in good agreement with the experiments. We discuss some future applications of laser aligned molecules.

Comparison of chemical selectivity and kinetic energy release in Si(s)+ICl(g) and H(g)+ICl(g)

ICl chemisorbs onto Si(111)–7×7 by two mechanisms: dissociative chemisorption and abstractive chemisorption. Abstractive chemisorption, in which one halogen atom of ICl bonds to the silicon surface while the other is ejected into the gas phase, is the dominant chemisorption mechanism for ICl/Si(111)–7×7. Multiphoton ionization (205 nm MPI) spectroscopy and time-of-flight (TOF) mass spectrometry were used to determine that the ratio of iodine-selective abstraction to chlorine-selective abstraction is at least 34±4: 1. The ICl and Si(111)–7×7 reaction can be compared to the ICl and atomic hydrogen (deuterium) reaction which has been studied extensively by others. The chemical selectivity of ICl+Si(111) is greater than the chemical selectivity of the gas phase reaction of H+ICl where the ratio of formation of HI to HCl is only 4:1. In both reactions, the iodine atom of ICl molecules is more reactive than the chlorine atom because the πx,y* antibonding orbital (the orbital that covalently reacts with other species) consists primarily of atomic iodine orbitals. The difference in the chemical selectivities of the silicon surface and gaseous hydrogen reactions with ICl is due to the ability of the silicon surface to rotationally steer ICl molecules, and the inability of silicon to migrate between the iodine and chlorine atoms. The median translational energies of ejected halogen atoms were determined to be 0.18±0.04 eV for chlorine atoms and 0.53±0.27 eV for iodine atoms which are a small fraction (14% for ejected iodine atoms and 9% for ejected chlorine atoms) of the total reaction exothermicities. The low translational energies of ejected atoms is due to the fact that the iodine–chlorine bond of ICl lengthens as the Si–I bond contracts; thus, there is little repulsion energy attributed to the Si–I–Cl transition state.

Photodissociation of ICl Molecule Oriented by an Intense Electric Field: Experiment and Theoretical Analysis

The idea of orienting molecules by applying an intense electric field on a rotationally very cold molecular beam has been introduced in 1990 by Loesch and Remscheid (J. Chem. Phys. 1990, 93, 4779) and also by Friedrich and Herschbach (Z. Phys. D 1991, 18, 153). Here we describe an experiment in which the orientation thus produced in ICl molecules is tested by a photodissociation experiment. The paper discusses the orientation process with emphasis on the effects nonlinear in the applied electric field. The characterization of the oriented beam and the experiment will be briefly described. A complete simulation leads to a very good fit of the observed signal, but the rotational temperature deduced from this fit is higher than given by a direct measurement, the discrepancy being due to the presence of van der Waals complexes. This experiment has provided the first direct measurement (Chem. Phys. Lett. 1995, 244, 195) of the sign of the dipole of ICl (I+Cl- as expected) and a measurement of the strong orientation achieved.

Reactive Scattering of OD Radicals with ICl and Br2 Molecules at Initial Translational Energy E ∼ 90 kJ mol-1

Reactive scattering of OD radicals with ICl and Br2 molecules has been studied at an initial translational energy E ∼ 90 kJ mol-1 using a supersonic beam of OD radicals seeded in He buffer gas generated from a high-temperature radio frequency discharge source. The center-of-mass angular distribution of DOI scattering from OD + ICl shows sharp forward and backward peaking with the relative intensity of the backward peak being lower by a factor ∼0.6 ± 0.1. The DOBr scattering from OD + Br2 shows broader peaking in the forward direction declining to a lower intensity ∼0.8 ± 0.2 in the backward direction. In both cases the product translational energy distributions peak at low energy with a tail extending out to higher energy. Comparison with the predictions of phase space theory indicates that the OD + ICl reaction proceeds via a DOICl collision complex with a lifetime of approximately one rotational period, while the OD + Br2 reaction shows evidence for the migration of the OD radical between the Br atoms of a DOBrBr complex. The DOICl complex corresponds to a significant well of depth E0 ∼ 80 kJ mol-1 on the potential energy surface for the OD + ICl reaction while the potential energy surface for the OD + Br2 reaction also supports a shallow minimum.