Stretching Vibration Mode Research Articles

Surprising photochemical reactivity and visible light-driven energy transfer in heterodimetallic complexes

The bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) has been used for the synthesis of a series of novel heterodimetallic complexes starting from [Ru(bpy)(2)(dppcb)]X(2) (1; X = PF(6), SbF(6)), so-called dyads, showing surprising photochemical reactivity. They consist of [Ru(bpy)(2)](2+)"antenna" sites absorbing light combined with reactive square-planar metal centres. Thus, irradiating [Ru(bpy)(2)(dppcb)MCl(2)]X(2) (M = Pt, 2; Pd, 3; X = PF(6), SbF(6)) dissolved in CH(3)CN with visible light, produces the unique heterodimetallic compounds [Ru(bpy)(CH(3)CN)(2)(dppcb)MCl(2)]X(2) (M = Pt, 7; Pd, 8; X = PF(6), SbF(6)). In an analogous reaction the separable diastereoisomers (ΔΛ/ΛΔ)- and (ΔΔ/ΛΛ)-[Ru(bpy)(2)(dppcb)Os(bpy)(2)](PF(6))(4) (5/6) lead to [Ru(bpy)(CH(3)CN)(2)(dppcb)Os(bpy)(2)](PF(6))(4) (9), where only the RuP(2)N(4) moiety of 5/6 is photochemically reactive. By contrast, in the case of [Ru(bpy)(2)(dppcb)NiCl(2)]X(2) (4; X = PF(6), SbF(6)) no clean photoreaction is observed. Interestingly, this difference in photochemical behaviour is completely in line with the related photophysical parameters, where 2, 3, and 5/6, but not 4, show long-lived excited states at ambient temperature necessary for this type of photoreaction. Furthermore, the photochemical as well as the photophysical properties of 2-4 are also in accordance with their single crystal X-ray structures presented in this work. It seems likely that differences in "steric pressure" play a major role for these properties. The unique complexes 7-9 are also fully characterized by single-crystal X-ray structure analyses, clearly showing that the stretching vibration modes of the ligand CH(3)CN, present only in 7-9, cannot be directly influenced by "steric pressure". This has dramatic consequences for their photophysical parameters. The trans-[Ru(bpy)(CH(3)CN)(2)](2+) chromophore of 9 acts as efficient "antenna" for visible light-driven energy transfer to the Os-centred "trap" site, resulting in k(en) ≥ 2 × 10(9) s(-1) for the energy transfer. Since electron transfer is made possible by the use of this intervening energy transfer, in dyads like 2-4 highly reactive M(0) species (M = Pt, Pd, Ni) could be generated. These species are not stable in water and M(II) hydride intermediates are usually formed, further reacting with H(+) to give H(2). Thus, derivatives of 3, namely [M(bpy)(2)(dppcb)Pd(bpy)](PF(6))(4) (M = Os, Ru) dissolved in 1:1 (v/v) H(2)O-CH(3)CN produce H(2) during photolysis with visible light.

Temperature-dependent Raman scattering of multiferroicPb(Fe1/2Nb1/2)O3

Raman scattering measurements on multiferroicPb(Fe1/2Nb1/2)O3 over a wide temperature range from 10 to 500 K were performed. Very broad andoverlapping peaks (first-order character) and a prominent high-frequency peak at ∼ 1130 cm − 1, which we assign as a two-phonon peak, were observed. These features showed remarkablechanges in their Raman scattering intensity and spectral shape at the characteristic temperatureT* ∼ 330 K, clearly showing a structural lattice change at aroundT*. The temperature dependence of some stretching vibration modes of theBO6 units revealed an anomalous frequency shift belowTN ∼ 143 K. These anomalousdeviations at TN of the phonon frequency are associated with the spin–phonon couplingmechanism. Complementary magnetic data confirmed a weak magneticordering at room temperature and interestingly showed an anomaly at aboutT*. These results suggest an interplay between ferroelectric, structural andmagnetic degrees of freedom in PFN, starting to be significant at aroundT*.

Photo‐induced phase switching dynamics in RbMn[Fe(CN)6] probed by accumulation free mid‐infrared spectroscopy

AbstractPhoto‐induced phase switching dynamics in rubidium manganese hexacyanoferrate was investigated by visible pump mid‐infrared probe transmittance spectroscopy between 2000 and 2250 cm−1. We monitored the CN− stretching vibration modes, which are sensitive to the valence states of the adjacent metal ions, to observe the transient changes of the valences. Accumulation free method was applied to this measurement to remove the persistent phase transition and maintain the initial state constant for every pump pulse. At low temperature, the sample in low temperature phase (LTP) is irradiated with 532 nm light to stimulate intervalence charge transfer (Fe2+ → Mn3+) band, and photoinduced high temperature phase (PI‐HTP), whose properties are similar to that of HTP, is created. The PI‐HTP is reversed to LT phase by irradiating with 400 nm light which stimulates ligand‐to‐metal charge transfer (CN− → Fe3+) band. In the photoinduced phase transition (PIPT) process from PI‐HTP to LTP, increase of the valence pairs corresponding to the phase boundary state resulting from the charge transfer, CN− to Fe3+, was clearly observed. The transient change has a rising time of shorter than 1 ps and a decay time longer than 100 ps. In the reverse process i.e., LTP to PI‐HTP, reduction of LTP and production of boundary state induced by the charge transfer, Fe2+ to Mn3+, were observed. These changes appeared within 1 ps and survived more than 100 ps.

Physical properties of chemical vapour deposited nanostructured carbon thin films

A simple thermal chemical vapour deposition technique is employed for the deposition of carbon films by pyrolysing the natural precursor “turpentine oil” on to the stainless steel (SS) and FTO coated quartz substrates at higher temperatures (700–1100 °C). In this work, we have studied the influence of substrate and deposition temperature on the evolution of structural and morphological properties of nanostructured carbon films. The films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurements, Fourier transform infrared (FTIR) and Raman spectroscopy techniques. XRD study reveals that the films are polycrystalline exhibiting hexagonal and face-centered cubic structures on SS and FTO coated glass substrates respectively. SEM images show the porous and agglomerated surface of the films. Deposited carbon films show the hydrophobic nature. FTIR study displays C–H and O–H stretching vibration modes in the films. Raman analysis shows that, high ID/IG for FTO substrate confirms the dominance of sp 3 bonds with diamond phase and less for SS shows graphitization effect with dominant sp 2 bonds. It reveals the difference in local microstructure of carbon deposits leading to variation in contact angle and hardness, which is ascribed to difference in the packing density of carbon films, as observed also by Raman.

Synthesis, photophysics and excited state structure of 1,8-di(p-tolyl)-1,3,5,7-octatetrayne

The Cadiot–Chodkiewicz type C2-elongation of p-tolylacetylene followed by dimerization of the resulted diyne p-CH3C6H4(CC)2TMS (1) gave thermally stable octatetrayne p-CH3C6H4(CC)4-p-C6H4CH3 (2) as light yellow powder in 75% yield. Compound 2 was characterized by spectroscopic methods and X-ray crystallography. Careful analysis of the crystal data revealed high degree of chain linearity with a potential for 1,n-topochemical polymerization. Next, photophysical properties of 2 were studied in details by experimental and advanced theoretical methods (ab initio HF as well as DFT calculations involving both the ground and excited state geometry optimization). These properties are similar to the properties of the parent polyyne C6H5(CC)4C6H5 previously described in literature (in particular, the lowest electronic excited singlet state (S1) of 2 is a dark state). This was confirmed by the experimental facts, namely, few progressions of the stretching mode (ag) of the polyyne chain, starting from different “false origins” lying below the second excited (bright) state (S2), were observed in the fluorescence excitation spectrum. The red shift of the electronic spectra (155cm−1 and 300cm−1 for absorption and fluorescence, respectively) and an increase of an energy gap between S1 and S2 states by 450cm−1 are the effects of methylation of C6H5(CC)4C6H5 to 2. Theoretical results showed that in the excited state of 2 a shortening of single bonds and elongation of triple bonds occurred. This is in accordance with an observation of a long progression of the stretching vibration mode in the experimental absorption spectrum of 2. Besides that, stretching vibration of the polyyne chain is also active in the fluorescence spectra.

Microcalorimetric and FTIR Study of the Adsorption of Carbon Dioxide on Alkali-Metal Exchanged FER Zeolites

Adsorption of CO2 on alkali-metal exchanged (Li+, Na+, K+) FER zeolites was investigated by means of microcalorimetry and FTIR spectroscopy. The adsorption enthalpies strongly depend on coverage for all investigated materials and they are also influenced by concentration of Al in the framework. Especially, samples of Na- and K-FER with lower Si/Al ratio (8.6) exhibited substantially larger initial interaction energy than samples with Si/Al 27.5. Differences in zero-coverage adsorption energy of zeolites with different cation concentration (Si/Al ratio) are 9 and 7.2 kJ/mol for Na- and K-FER zeolites respectively. This phenomenon is attributed to formation of bridged CO2 adsorption complexes formed between two cations, which are characterized by IR absorption band of ν3 stretching vibration mode at 2370 and 2357 cm−1 for Na- and K-FER respectively.

Highly Strained Compliant Optical Metamaterials with Large Frequency Tunability

Metamaterial designs are typically limited to operation over a narrow bandwidth dictated by the resonant line width. Here we report a compliant metamaterial with tunability of Δλ ∼ 400 nm, greater than the resonant line width at optical frequencies, using high-strain mechanical deformation of an elastomeric substrate to controllably modify the distance between the resonant elements. Using this compliant platform, we demonstrate dynamic surface-enhanced infrared absorption by tuning the metamaterial resonant frequency through a CH stretch vibrational mode, enhancing the reflection signal by a factor of 180. Manipulation of resonator components is also used to tune and modulate the Fano resonance of a coupled system.

Synthesis of 18O-labeled photosynthetically active chlorophylls at the 3- or 7-carbonyl group with high regioselectivity

The 3- and 7-formyl groups of chlorophyll-d (Chl-d) and bacteriochlorophyll-e (BChl-e), respectively, were regioselectively labeled with an isotopically stable oxygen-18 (¹⁸O) atom to give 3¹-¹⁸O-labeled Chl-d and 7¹-¹⁸O-labeled BChl-e (ca. 90% ¹⁸O) by exchanging the carbonyl oxygen atoms in the presence of acidic H₂ ¹⁸O (ca. 95% ¹⁸O). Another photosynthetically active chlorophyll, BChl-a possessing the 3-acetyl group was treated under similar acidic conditions to afford a trace amount of 3¹-¹⁸O-labeled BChl-a and further demetallated compound, the corresponding 3¹-¹⁸O-labeled bacteriopheophytin-a as the major product with 55% ¹⁸O-degree. The FT-IR spectra of ¹⁸O-(un)labeled chlorophylls in the solution and the solid states showed that the 3- and 7-carbonyl stretching vibration modes moved to about a 30-cm⁻¹ lower wavenumber by ¹⁸O-labeling at the 3¹- and 7¹-oxo moieties. In artificial chlorosome-like self-aggregates of BChl-e, the ¹⁸O-labeled 7-carbonyl stretching mode was completely resolved from the specially hydrogen-bonded 13-C=O stretching mode, evidently indicating no interaction of the 7-CHO with other functional groups in the supramolecules.

A Conformation and Orientation Model of the Carboxylic Group of Fatty Acids Dependent on Chain Length in a Langmuir Monolayer Film Studied by Polarization-Modulation Infrared Reflection Absorption Spectroscopy

The conformation of the carboxylic group of fatty acids in a Langmuir (L) monolayer film on water is described in relation to the aggregation property of the hydrocarbon chain. Polarization-modulation infrared reflection absorption spectra (PM-IRRAS) of L films of heptadecanoic acid (C(17)), octadecanoic acid (C(18)), and nonadecanoic acid (C(19)) exhibit systematic spectral changes in both the C-H and C=O stretching vibration regions. Through a stabilization analysis of the L films at a high surface pressure, the C(19) L film has been found outstandingly stable exhibiting no film shrink, while the other two compounds exhibit a large shrink at high surface pressure. By taking into account the uniquely high aggregation property of the hydrocarbon chains of C(19), the three major bands arising from the C=O stretching vibration mode propose three types of molecular conformations about the carboxylic group, which are elucidated by a balance of the hydration of the carboxylic group, the chain length of the hydrocarbon chain, and the surface pressure.

Hydrogen vibrational modes on graphene and relaxation of the C–H stretch excitation from first-principles calculations

Density functional theory (DFT) calculations are used to determine the vibrational modes of hydrogen adsorbed on graphene in the low-coverage limit. Both the calculated adsorption energy of a H atom of 0.8 eV and calculated C-H stretch vibrational frequency of 2552 cm(-1) are unusually low for hydrocarbons, but in agreement with data from electron energy loss spectroscopy on hydrogenated graphite. The clustering of two adsorbed H atoms observed in scanning tunneling microscopy images shows its fingerprint also in our calculated spectra. The energetically preferred adsorption on different sublattices correlates with a blueshift of the C-H stretch vibrational modes in H adatom clusters. The C-H bending modes are calculated to be in the 1100 cm(-1) range, resonant with the graphene phonons. Moreover, we use our previously developed methods to calculate the relaxation of the C-H stretch mode via vibration-phonon interaction, using the Born-Oppenheimer surface for all local modes as obtained from the DFT calculations. The total decay rate of the H stretch into other H vibrations, thereby creating or annihilating one graphene phonon, is determined from Fermi's golden rule. Our calculations using the matrix elements derived from DFT calculations show that the lifetime of the H stretch mode on graphene is only several picoseconds, much shorter than on other semiconductor surfaces such as Ge(001) and Si(001).

Polarized Raman scattering study of blue bronze Tl 0.3MoO 3

Temperature dependent polarized Raman spectra of quasi-one dimensional blue bronze Tl 0.3MoO 3 are reported on a frequency range 100–1100 cm −1. Frequency shift and splitting in some modes were observed, revealing the role of the alkali atom. Many new modes emerge at 170 K accompanied by charge density wave (CDW) formation, and show gradual temperature dependent intensity and line-width, implying the second order nature of CDW transition. A frequency “jump” is found for many Raman vibrational modes in Tl 0.3MoO 3 near 110 K, confirming that the transition from an incommensurate to commensurate state occurs around this temperature. In addition, only three stretching vibration modes of terminal MoO bonds are observed for (xx) polarizations from 800 to 1100 cm −1 at 300 K; new modes appear only when the temperature drops below 110 K and are ascribed to the splitting of the mode at 931 cm −1 due to commensurate state formation.

Raman spectra of ice and salt hydrates in synthetic fluid inclusions

Raman spectra of ice, NaCl·2H 2O (hydrohalite), CaCl 2·6H 2O (antarcticite), α -CaCl 2·4H 2O, γ-CaCl 2·4H 2O, CaCl 2·2H 2O (sinjarite), MgCl 2·12H 2O, FeCl 2·6H 2O, FeCl 2·4H 2O, and a LiCl hydrate are characterized in synthetic fluid inclusions in quartz at about − 190 °C. Each hydrate can be distinguished on its characteristic Raman bands, which occur at wavenumbers in the range of the stretching vibration mode of water (2800 to 4000 cm − 1 ). The spectra provide the basis for the interpretation of Raman spectra obtained in natural fluid inclusions.

On the origin of the Raman band shifts for H-bonded complexes of normal alcohols and 2-butoxyethanol with water: A theoretical DFT and MP2 study

The present theoretical study discusses the origin of the Raman band shifts appeared in the C–H stretching vibration region for complexes of normal alcohols with water as well as those of 2-butoxyethanol. It was shown that the nature of the red shift in the Raman active C–H stretching vibration modes initiated by a nanosecond temperature jump has a novel interpretation and bolster further the previously observed phenomenon for triethylamine–water complex.

Infrared Spectra of Mass-Selected Br−−(NH3)n and I−−NH3 Clusters

Infrared vibrational predissociation spectra are recorded for Br(-)-(NH(3))(n) (n = 1-4) and I(-)-NH(3) clusters in the N-H stretch region (3040-3460 cm(-1)). To aid spectral assignments and clarify structures of the Br(-)-(NH(3))(n) clusters, ab initio calculations are performed at the MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ levels of theory. The Br(-)-NH(3) and I(-)-NH(3) dimers are predicted to have structures in which the NH(3) molecule is attached to the halide anion by a single hydrogen-bond. The dominant infrared band for Br(-)-NH(3) at 3171 cm(-1) corresponds to a hydrogen-bonded N-H stretch vibrational mode, whereas two weaker bands are assigned to a symmetric stretch vibration of the nonbonded N-H groups (3347 cm(-1)) and to an ammonia-based bending overtone (3293 cm(-1)) deriving infrared intensity through Fermi interaction with the H-bonded N-H stretch mode. The corresponding I(-)-NH(3) spectrum is dominated by the H-bonded N-H stretch band at 3217 cm(-1), with three weaker bands at 3240, 3305, and 3360 cm(-1) assigned to two bending overtone vibrations and the nonbonded N-H symmetric stretch vibration, respectively. Spectra of the Br(-)-(NH(3))(n), n = 2-4, clusters are similar to the I(-)-NH(3) spectrum, exhibiting evidence for strong Fermi interactions between the H-bonded N-H stretch vibrational mode and ammonia-based bending overtones. On the basis of the infrared spectra and ab initio calculations, the larger Br(-)-(NH(3))(n) clusters are deduced to have structures in which the NH(3) molecules are attached to the Br(-) by single H-bonds, but not necessarily to one other.

N‐Heterocyclic Carbene (NHC)‐Stabilized Silanechalcogenones: NHC→Si(R2)E (E=O, S, Se, Te)

A series of N-heterocyclic carbene-stabilized silanechalcogenones 2 a,b (Si=O), 3 a,b (Si=S), 4 a,b (Si=Se), and 5 a,b (Si=Te) are described. The silanone complexes 2 a,b were prepared by facile oxygenation of the carbene-silylene adducts 1 a,b with N(2)O, whereas their heavier congeners were synthesized by gentle chalcogenation of 1 a,b with equimolar amounts of elemental sulfur, selenium, and tellurium, respectively. These novel compounds have been isolated in a crystalline form in high yields and have been fully characterized by a variety of techniques including IR spectroscopy, ESIMS, and multinuclear NMR spectroscopy. The structures of 2 b, 3 a, 4 a, 4 b, and 5 b have been confirmed by single-crystal X-ray crystallography. Due to the NHC-->Si donor-acceptor electronic interaction, the Si=E (E=O, S, Se, Te) moieties within these compounds are well stabilized and thus the compounds possess several ylide-like resonance structures. Nevertheless, these species also exhibit considerable Si=E double-bond character, presumably through a nonclassical Si=E pi-bonding interaction between the chalcogen lone-pair electrons and two antibonding Si-N sigma* orbitals, as evidenced by their high stretching vibration modes and the shortening of the Si-E distances (between 5.4 and 6.3%) compared with the corresponding Si-E single-bond lengths.

Existence of dual species composed of Cu+ in CuMFI being bridged by C2H2

The interaction of ethyne (C(2)H(2)), as well as of carbon dioxide (CO(2)), with copper-ion-exchanged MFI zeolite (CuMFI) at room temperature was examined. It was found that CuMFI preferentially adsorbs C(2)H(2), while this material does not respond to CO(2). To clarify the specificity of CuMFI, a combination of various experimental techniques and theoretical calculations was adopted. Distinctive interaction energies of 140 and 110 kJ mol(-1) were clearly observed at the initial stage of C(2)H(2) adsorption on CuMFI, suggesting the presence of two types of adsorbed C(2)H(2). Two distinct IR bands at 1620 and 1814 cm(-1) appeared, which were assigned to the C[triple bond]C stretching vibration modes of C(2)H(2) differing in their adsorbed state. Both photoluminescence and X-ray absorption spectra showed that cuprous ions (Cu(+)) in CuMFI act as efficient sites for a marked C(2)H(2) adsorption. From the analysis of the latter spectra and the calculational results based on the density functional theory, the formation of dual Cu(+)...(C(2)H(2))...Cu(+) complexes was indicated for the first time for CuMFI, and such a special configuration of the Cu(+) sites contributed to the extremely strong adsorption of C(2)H(2). In contrast, it was necessary for the linear CO(2) molecule to take a bent structure to be adsorbed on Cu(+) in CuMFI. It was concluded that the difference in the adsorption response of Cu(+) in CuMFI towards C(2)H(2) and CO(2) is due to the chemistry between the nature of electron donation of Cu(+) and the hybrid orbitals of the respective molecules. This work promotes further understanding of the states of active centres in CuMFI for C(2)H(2) activation, as well as for N(2) fixation.

An investigation of slow charge separation in a Tyrosine M210 to Tryptophan mutant of the Rhodobacter sphaeroides reaction center by femtosecond mid-infrared spectroscopy

Energy and electron transfer in a tyrosine M210 to tryptophan (YM210W) mutant of the Rhodobacter sphaeroides reaction center (RC) were investigated through time-resolved visible pump/mid-infrared (mid-IR) probe spectroscopy at room temperature, with the aim to further characterize the primary charge separated states in the RC. This mutant is known to display slow and multi-exponential charge separation, and was used in earlier work to prove the existence of an alternative route for charge separation starting from the accessory bacteriochlorophyll in the active branch, B(L). The mutant RCs were excited at 860 nm (direct excitation of the primary donor (P) BChls (P(L)/P(M))), 600 nm (unselective excitation), 805 nm (direct excitation of both accessory bacteriochlorophyll cofactors B(L) and B(M)) and 795 nm (direct excitation of B(L)). Absorption changes associated with carbonyl (C=O) stretch vibrational modes of the cofactors and protein were recorded in the region between 1600 and 1775 cm(-1), and both a sequential analysis and simultaneous target analysis of the data were performed. The decay of P* in the YM210W mutant was multi-exponential with lifetimes of 29 and 63.5 ps. The decay of P(+)B(L)(-) state was approximately 10 times longer in the YM210W RC than in the R-26 RC (approximately 7 ps vs. approximately 0.7 ps), and in the mid-IR difference absorption spectrum of P(+)B(L)(-) the stretching frequency of the 9-keto C=O group of B(L) in the ground state was located around 1675-1680 cm(-1), consistent with the presence of a hydrogen bond donated by an adjacent water molecule. Excitation at 795 nm produced a small amount of B(L)*-driven charge separation, as assessed from the excitation wavelength dependence of the raw difference spectra recorded during the first few ps after excitation. This process led to the formation of P(+)B(L)(-). Only the relaxed form of the P(+)H(L)(-) radical pair was observed in the YM210W mutant, and the mid-IR difference absorption spectra of P(+)H(L)(-) and P(+)B(L)(-) showed a change in the relative amplitude of the P(L)(+) and P(M)(+) bands when compared to equivalent spectra for the R-26 RC. This indicates that the YM210W mutation causes an increased localization of the electron hole on the P(M) half of the dimer. The absorbance difference spectrum of P(+)H(L)(-) in the R-26 RC contains a feature attributable to a Stark shift of one or more amide C=O oscillators. This feature was shifted to lower frequency by approximately 5 cm(-1) in the YM210W RC, and consideration of the limited structural changes in this RC indicates that this feature arises from an amide C=O group in the immediate vicinity of the M210 residue, most probably that of the adjacent M209 amino acid.

Structure and properties of the Zn+–D2 complex

The infrared spectrum of the (66)Zn(+)-D(2) complex is measured in the D-D stretch region (2815-2866 cm(-1)) by detecting Zn(+) photofragments. The spectrum is consistent with the Zn(+)-D(2) complex consisting of a slightly distorted D(2) molecule attached to a ground state Zn(+) ion in a T-shaped equilibrium configuration. From the rotational constants, the vibrationally averaged intermolecular bond length is deduced to be 2.32 A, contracting by 0.02 A upon excitation of the D-D stretch vibrational mode. The band center of the D-D stretch transition is shifted by -154.8 cm(-1) from the Q(0) (1) transition of the free D(2) molecule. Density functional theory calculations are performed to elucidate the molecular bonding in the complex. The current spectroscopic and calculated data for Zn(+)-D(2), together with the previously determined binding energy for Zn(+)-H(2) [1310 cm(-1); P. Weis, et al., J. Phys. Chem. A 101, 2809 (1997)], result in a comprehensive characterization of the Zn(+)-D(2) and Zn(+)-H(2) complexes.

The Cr+–D2 cation complex: Accurate experimental dissociation energy, intermolecular bond length, and vibrational parameters

The infrared spectrum of the T-shaped (52)Cr(+)-D(2) complex is measured over the 2742-2820 cm(-1) range by detecting Cr(+) photofragments. The main band, due to the D-D stretch excitation, is shifted at 215 cm(-1) to lower energy from the Q(0) (1) transition of the free D(2) molecule and displays clearly resolved rovibrational transitions. Observation of a photodissociation onset for the N(')=8 rotational level is used to infer that the dissociation energy of Cr(+)-D(2), with respect to ground-state Cr(+) and D(2) fragments, lies between 2839.7 and 2856.9 cm(-1). Perturbations to the upper state levels are presumed to arise from interactions with quasibound combination levels involving the intermolecular stretch and bend vibrational modes. A vibrationally averaged Cr(+)...D(2) separation of 2.023 A and an estimate of 394 cm(-1) for the intermolecular harmonic stretching frequency are derived from the measured rotational constants.

Recharging processes, radiation induced strain and changes of OH − bands under H + ion implantation in Ti doped lithium niobate

A systematic analysis of variations in structural and optical characteristics of Z-cut plates of titanium doped congruent lithium niobate single crystals implanted with 120 keV proton beam at various fluences of 10 15, 10 16 and 10 17 protons/cm 2 is presented. Through, high resolution X-ray diffraction, atomic force microscopy, Fourier transform infrared and UV–visible–NIR analysis of congruent lithium niobate, the correlation of properties before and after implantation are discussed. HRXRD (0 0 6) reflection by Triple Crystal Mode shows that both tensile and compressive strain peak are produced by the high fluence implantation. A distinct tensile peak was observed from implanted region for a fluence of 10 16 protons/cm 2. AFM micrographs indicate mountain ridges, bumps and protrusions on target surface on implantation. UV–visible–NIR spectra reveal an increase in charge transfer between Ti 3+/Ti 4+ and ligand oxygen for implantation with 10 15 protons/cm 2, while spectra for higher fluence implanted samples show complex absorption band in the region from 380–1100 nm. Variations of OH − stretching vibration mode were observed for cLN Pure, cLNT2% virgin, and implanted samples with FTIR spectra. The concentration of OH − ion before and after implantation was calculated from integral absorption intensity. The effect of 120 keV proton implantation induced structural, surface and optical studies were correlated.