Ν3 Band Research Articles

Analysis of the High-Resolution Spectrum of Molecules in Doublet Electronic States: Fundamental ν3 Band of Chlorine Dioxide (16O35Cl16O) in the Ground Electronic State X 2B1

Analysis of the High-Resolution Spectrum of Molecules in Doublet Electronic States: Fundamental ν3 Band of Chlorine Dioxide (16O35Cl16O) in the Ground Electronic State X 2B1

Determination of temperature-dependent Fermi resonance in acetonitrile-water binary solution by two-dimensional correlation Raman spectroscopy.

Acetonitrile (AN), as an organic solvent, has a wide range of applications. The C≡N stretching vibration mode (ν2) and the combination mode (ν3 + ν4) are coupled by Fermi resonance (FR). In this work, the phase transition and the interaction mechanism of the 60% AN-water binary solution (AN-Water) were analyzed by calculating FR parameters and two-dimensional correlation Raman spectroscopy (2DCRS). The change in the ν2 band and the base bands ν3 and ν4 caused energy transfer by anharmonic interaction, which led to a change in FR parameters. With a reduced temperature, the energy transfer was caused by microheterogeneity and the energy transfer effect (293-273K), the phase separation (263-233K), and the phase transition of AN (223-173K). The 2DCRS and Gaussian deconvolution provided more information on FR, which revealed the interaction mechanism of the Fermi doublet. The polarity and binding modes of molecules provided a new perspective for analyzing the transmission of electrons and ions in the electrolyte at different temperatures.

The vibrational properties of benzene on an ordered water ice surface

ABSTRACT We present a hybrid CCSD(T) + PBE-D3 approach to calculating the vibrational signatures for gas-phase benzene and benzene adsorbed on an ordered water ice surface. We compare the results of our method against experimentally recorded spectra and calculations performed using PBE-D3-only approaches (harmonic and anharmonic). Calculations use a proton ordered XIh water ice surface consisting of 288 water molecules, and results are compared against experimental spectra recorded for an ASW ice surface. We show the importance of including a water ice surface into spectroscopic calculations, owing to the resulting differences in vibrational modes, frequencies, and intensities of transitions seen in the IR spectrum. The overall intensity pattern shifts from a dominating ν11 band in the gas-phase to several high-intensity carriers for an IR spectrum of adsorbed benzene. When used for adsorbed benzene, the hybrid approach presented here achieves an RMSD for IR active modes of 21 cm−1, compared to 72 cm−1 and 49 cm−1 for the anharmonic and harmonic PBE-D3 approaches, respectively. Our hybrid model for gaseous benzene also achieves the best results when compared to experiment, with an RMSD for IR active modes of 24 cm−1, compared to 55 cm−1 and 31 cm−1 for the anharmonic and harmonic PBE-D3 approaches, respectively. To facilitate assignment, we generate and provide a correspondence graph between the normal modes of the gaseous and adsorbed benzene molecules. Finally, we calculate the frequency shifts, Δν, of adsorbed benzene relative to its gas-phase to highlight the effects of surface interactions on vibrational bands and evaluate the suitability of our chosen dispersion-corrected density functional theory.

Effects of sintering temperature on microstructure, initial permeability and electric behaviour of Ni-Mn-Zn ferrites

The effects of sintering temperature on microstructure, initial permeability, and electrical behaviour of Ni0.5-xMnxZn0.5Fe2O4 (0.0 < x < 0.5) prepared using the precursor combustion method have been investigated. X-ray diffraction analysis confirmed the single phase cubic spinel structure of Ni0.5-xMnxZn0.5Fe2O4 (0.0 < x < 0.4) compositions sintered at 1100 °C. The Mn2+ substituent preferentially occupies tetrahedral sites as indicated by the Rietveld analysis and the increase in the IR absorption frequency of ν1 band with increasing Mn substitution. The SEM measurements have revealed homogeneous microstructures of the ferrites with narrow grain size distribution in the range 0.93μm–1.86 μm. Mössbauer spectra exhibit a superposition of two Zeeman sextets for the compositions x ≤ 0.2, a superposition of two Zeeman sextets, and a paramagnetic doublet for the compositions, x = 0.3 and 0.4, and one sextet and single quadrupole doublet for a composition, x = 0.5. The activation energy in the range 0.258 eV–0.612 eV suggests a polaron hopping type conduction mechanism in all the sintered ferrites. The dielectric constant in the range 0.057–55.21 and lower dielectric loss (10−2) imply better stoichiometry and homogeneity. The initial permeability increases at lower Mn substitution (x = 0.2) and exhibits a decrease as the Mn substitution increases. The dc resistivity, dielectric constant, and initial permeability values suggest the suitability of these ferrites for high frequency device applications.

Beryl crystal chemistry and trace elements: Indicators of pegmatite development and fractionation (Damara Belt, Namibia)

The study reveals the relationships between crystal-chemical and genetic properties of beryl from several rare-element granitic pegmatites of the LCT family from the Damara Belt, Namibia. Based on their chemical compositions, the studied beryl samples can be divided into two groups. Beryl from the first group (the Engelbrecht's and Etusis pegmatites) is poor in Fe, Mg and Mn; however, slightly enriched in Zn and alkali elements (Na > Li, Rb, Cs). The samples from the second group (Kuduberge and Tsaobismund) are slightly enriched in Fe and Mg, in which they are mostly charge-balanced by Na, while other octahedral and channel constituents are negligible. The affinity of the first group of beryl to the dominant tetrahedral substitution is manifested in cell dimensions and the c/a ratio. Based on Raman and infrared spectroscopy, the Kuduberge and Tsaobismund samples have a very similar position and intensity of water FTIR bands, indicating the presence of both water types in the channels. The Englebrecht's sample is similar, however, the Etusis sample exhibits a shift of H2O II ν1 band, which could be attributed to a smaller Na content and strong dominance of doubly coordinating water. Our results indicate preferential occupancy of Na in the octahedral Na + (Fe,Mg)2+ = + Al substitution, which is typical for beryl from less fractionated pegmatites (Kuduberge and Tsaobismund), however, Na can also be a part of the complex tetrahedral substitution found in Englebrecht's beryl. Higher concentrations of Mn, Sc and Ti indicate a less fractionated genetic environment due to their affinity to Mg and Fe2+, whereas Cs, Rb and Zn prefer tetrahedral substitution, which is typical in highly evolved pegmatites.

The update of the line positions and intensities in the line list of carbon dioxide for the HITRAN2020 spectroscopic database

This paper describes the updates of the line positions and intensities for the carbon dioxide transitions in the 2020 edition of the HITRAN spectroscopic database. The new line list for all 12 naturally abundant isotopologues of carbon dioxide replaces the previous one from the HITRAN2016 edition. This update is primarily motivated by several issues related to deficient HITRAN2016 line positions and intensities that have been identified from laboratory and atmospheric spectra. Critical validation tests for the spectroscopic data were carried out to find problems caused by inaccuracies in CO2 line parameters. New sources of data were selected for the bands that were deemed problematic in the HITRAN2016 edition. Extra care was taken to retain the consistency in the data sources within the bands. The comparisons with the existing theoretical and semi-empirical databases (including ExoMol, NASA Ames, and CDSD-296) and with available experimental works were carried out. The HITRAN2020 database has been extended by including additional CO2 bands above 8000 cm−1, and magnetic dipole lines of CO2 were introduced in HITRAN for the first time by including the ν2+ν3 band in the 3.3-µm region. Although the main topic of this article is line positions and intensities, for consistency a recent algorithm for the line-shape parameters proposed in Hashemi et al. JQSRT (2020) was reapplied (after minor revisions) to the line list.

Line intensities and self-broadening coefficients of CH3I in the region of ν5 and ν3+ν6 bands

Systematic measurements of self-broadening coefficients for 992 transitions in the ν5 and ν3+ν6 perpendicular bands of CH3I up to the quantum numbers 3 ≤ J ≤ 52 and 0 ≤ K ≤ 12 have been performed for the first time using a mono-spectrum fitting technique utilizing a Voigt profile. Our previous line intensity measurements [Boughdiri, et al., JQSRT 221 (2018) 147-154] are also extended using new spectra recorded at room temperature at five pressures from 1.15 to 9.98 mbar using the Bruker IFS125HR Fourier Transform spectrometer at the AILES beamline of the SOLEIL Synchrotron facility. The measured absolute intensities were used to derive the transition dipole moment squared for each line, the band intensities as well as the Herman–Wallis coefficients. The rotational dependences of the self-broadening coefficients have been clearly observed and modeled. The data were compared with previous works. The results are given as supplementary data table for a possible use in atmospheric and industrial applications.

Analysis of the [formula omitted], [formula omitted], [formula omitted] and the [formula omitted] bands of HT[formula omitted

We present the ν1+2ν2, ν2+ν3, ν1+ν3 and the 2ν2+ν3 bands of HT16O that have been analyzed for the first time using a high-resolution infrared spectrum of tritiated water vapour. The spectrum has been recorded from a custom-built light-pipe cell at room temperature using a Bruker 125HR Fourier-transform spectrometer at a resolution of.0075 cm−1.In the range from 4715 to 5300 cm−1, we report 446 new experimental line positions assigned to the ν1+2ν2 and 611 new line positions belonging to the ν2+ν3 band.In the range of 5830 to 6440 cm−1, 165 new experimental line positions were determined for the ν1+ν3 band and 81 line positions were assigned to the 2ν2+ν3 band.The analysis reveals a systematic shift of the individual line positions compared to the variationally calculated line positions from the Tomsk database which uses the potential energy surface of Partridge and Schwenke. Furthermore, it is observed that the differences between prediction and experiment are depending on the rotational quantum number Ka′.For each band, the assigned lines were used to determine the spectroscopic constants in the A-reduced Watson Hamiltonian.With a total of 1303 new line positions for HT16O we roughly double the number of experimental line positions for this species.

Air-induced collisional parameters in the [formula omitted] band of methane

Air broadening and shift coefficients together with narrowing and first order line mixing parameters were measured for 166 lines belonging to J″ manifolds of the P (J″=2−11), Q (J″=1−12) and R (J″=0−11) branches of the ν3 band of 12CH4 near 3.3 μm. These measurements were carried out using a non-linear multispectrum least squares fitting technique. A hard collision Dicke narrowed line shape model including Rosenkranz line mixing was applied. Five high resolution Fourier transform spectra were recorded at room temperature, one at low pressure with pure methane and four at pressures up to 904 hPa with mixtures of methane and air. The measured parameters are compared with data available in the literature.

LA-ICPMS, TEM and Raman study of radiation damage, fluid-induced alteration and disturbance of U-Pb and Th-Pb ages in experimentally metasomatised monazite

Experimentally metasomatised monazite was studied in terms of preservation of U-Pb and Th-Pb ages during alkali-bearing fluid-induced alteration over a broad range of temperature conditions 250–750 °C. Starting materials for experiments included Burnet monazite (Concordia age 1100.5 ± 11.6 Ma, 2σ), albite, K-feldspar, biotite, muscovite, SiO2, CaF2, Na2Si2O5 and H2O. Monazite from experiments at 250–550 °C is partially replaced by secondary REE-rich fluorapatite [(Ca,LREE,Si,Na)5(PO4)3F], fluorcalciobritholite [(Ca,REE)5(SiO4,PO4)3F] and REE-rich steacyite [K1−x(Na,Ca)2(Th,U)Si8O20], and developed patchy zoning, whereas partial replacement by fluorcalciobritholite and cheralite [CaTh(PO4)2] occurred at 650 and 750 °C, with no signs of compositional alteration based on EPMA data and BSE imaging. Raman microspectroscopy results show narrowing of the ν1(PO4) stretching band in unaltered domains, which indicates advancing annealing of the monazite structure with increasing temperature, and narrow ν1(PO4) band with low FWHM values in altered domains. TEM investigations revealed that unaltered domains of monazite from experiments at 250–550 °C have mottled diffraction contrast, similar to the starting Burnet monazite, which indicates low to moderate degree of metamictization. On the contrary, the altered domains of monazite (patchy zones) show no mottled contrast, suggesting an ordered crystalline structure. TEM imaging demonstrated low degree of metamictization in monazite from the experiment at 650 °C; fluid-aided alteration along the cleavage planes resulted in the development of nanoporosity or partial replacement by fluorcalciobritholite and cheralite. Monazite from the experiment at 750 °C has crystalline structure with no signs of metamictization and shows significant development of nanoporosity and formation of secondary cheralite nanocrystals across the grain. For comparison, TEM and Raman evaluation of xenotime from similar experiments at 350 and 650 °C revealed that both starting xenotime and xenotime from experimental products are crystalline with no signs of radiation damage or fluid-induced alteration affecting internal domains on submicron scale, which could result in compositional alteration of the xenotime.The unaltered domains of monazite from runs at 250–550 °C yielded U-Pb and Th-Pb dates similar to the age of Burnet monazite, whereas altered domains yielded discordant dates due to various degree of Pb-loss (up to 99.4%). Linear regressions on the Concordia diagrams show lower intercept ages from −266 ± 160 Ma (run 350 °C, 200 MPa) to −1 ± 48 Ma (450 °C, 800 MPa), which reflect the “true age” of experimental alteration. The monazite from runs at 650 and 750 °C yielded data indicating initial disturbance of the U-Th-Pb system, ranging from 8.4% Pb-gain to 18.6% Pb-loss. Linear regressions with lower intercepts of −53 ± 420 Ma and −55 ± 610 Ma roughly correspond to the timing of the experiments. Furthermore, LA-ICPMS results demonstrate discrepancy between Th-Pb and U-Pb dates suggesting higher mobility of 208Pb than that of 207Pb and 206Pb.To summarize, TEM and Raman data indicate increasing annealing of the radiation damaged monazite with increasing temperature. Alteration processes induced by alkali-bearing fluid can result in recrystallization of monazite and various degrees of the age disturbance at temperatures 250–550 °C, whereas isotopic U-Th-Pb microanalysis provide an opportunity to constrain the age of the metasomatic processes as the lower intercept in the Concordia diagram. The particular importance of this study lies in submicron alteration of monazite at 650–750 °C induced by alkali-bearing fluid and/or melt, which remains unnoticed using common electron microscopy BSE imaging. Such alteration, however, induces substantial disturbance of U-Pb and Th-Pb ages, which can cause misinterpretations in reconstructions of geological processes.

Theoretical study of CH3Cl-N2 line shapes in the ν1 band. Line mixing effects in QR doublets and QQk sub-branches

Line coupling and line mixing effects of CH3Cl lines in the ν1 band perturbed by N2 have been investigated. We have taken into account the non-diagonality of the exp(−S2) operator within specified line spaces as well as the k-degeneracy of the transitions (due to the double degeneracy of the j,k levels with k ≠ 0). These transitions should be considered as doublets coupled by the line mixing process. A new problem appears in the calculation when the atom-atom potential model is introduced. In order to overcome this difficulty, a pragmatic approach is proposed. Comparisons of theoretically calculated matrix elements of W with measurements of QR(j,k) doublets as well as some QQk sub-branches, which are strongly affected by line mixing, have been made. The results show that the formalism improved in this way leads to rather accurate predictions.

The ν4 bands at 11 µm: linelists for the Trans- and Cis- conformer forms of nitrous acid (HONO) in the 2019 version of the GEISA database*

Using parameters of line positions and line intensities existing in the literature for the Trans- and Cis- conformer forms of nitrous acid (HONO), we generated, for the first time, a linelist of positions, intensities, and line shape parameters for the ν4 bands of nitrous acid located at 790.117 and 851.943 cm−1 for the Trans- and Cis- conformers, respectively. A validation of this linelist was performed using spectra recorded by the IASI (Interféromètre Atmosphérique de Sondage Infrarouge) satellite instrument in February 2009 during the (rather) exceptional conditions of the large Australian bush fires. This list, which is now included in the 2020 version of the GEISA database (https://geisa.aeris-data.fr/), is of potential interest for the IASI-NG (Infrared Atmospheric Sounding Interferometer – New Generation) instrument which will be launched on board the METOP-SG satellite in 2021.

Oxygen- and air-broadening coefficients for the CH[formula omitted]I [formula omitted] fundamental at room temperature

CH3I-oxygen line-broadening coefficients at 296 K are calculated for the RR, PR, RP, PP, RQ and PQ sub-branches of the ν6 band in a wide range of rotational quantum numbers (0≤J≤70, K≤20 by a semi-classical and a semi-empirical methods. The computed values compare very favourably with the available experimental data and therefore can be safely employed as estimates of broadening coefficients missing in databases for high J and K. The theoretical data for CH3I-O2 are further combined with the previously calculated room-temperature CH3I-N2 line-broadening coefficients to obtain the air-broadening values required for atmospheric applications. The calculated results demonstrate an excellent consistency with both existing sets of CH3I-air measurements. As the vibrational dependence of CH3I oxygen-broadening coefficients is shown to be small, similarly to the nitrogen-broadening case, the CH3I-O2 and CH3I-air line-broadening coefficients calculated for the ν6 fundamental can be used for other perpendicular and parallel bands.

High-resolution Fourier transform infrared (FTIR) spectroscopy of formaldoxime-13C (13CH2NOH): Ground and [formula omitted] states rovibrational constants

The high-resolution Fourier transform infrared (FTIR) spectrum of formaldoxime-13C (13CH2NOH) was recorded in the 840–930 cm−1 region with an unapodized resolution of 0.0019 cm−1 for a rovibrational analysis. In the analysis of the dominantly A-type ν8 band, a total of 1025 infrared transitions were fitted using the Watson's A-reduced and S-reduced Hamiltonians in the Ir representation with a root-mean-square (rms) deviations of 0.000430 cm−1 and 0.000431 cm−1 respectively. From the rovibrational analysis, the ν8 = 1 states rotational constants (A, B and C), five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) and one sextic term (ΦKJ) were derived for the first time. The band center of the ν8 band of 13CH2NOH was found to be 890.235170(25) cm−1 and 890.235182(25) cm−1 in the A-reduced and S-reduced Hamiltonians respectively. Ground state rovibrational constants except for rotational constants B and C were obtained for the first time through the fitting of 443 ground state combination differences (GSCDs) derived from the infrared transitions of the ν8 band of 13CH2NOH, together with 2 previously reported microwave frequencies. The rms deviation of the GSCD fits was the same at 0.000430 cm−1 for both A-reduced and S-reduced Hamiltonians. Furthermore, rovibrational constants up to 5 quartic centrifugal distortion terms of the ground state, and the band center and rotational constants (A, B and C) of the ν8 = 1 state were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set. Good agreement was found between the experimental and calculated rovibrational constants of 13CH2NOH for both ground and ν8 = 1 states.

New Insight into the Relationships Between Structural and Ftir Spectroscopic Features of Kaolinites

AbstractTo resolve the existing ambiguities in the interpretation of the OH-stretching vibrations of kaolinites, relationships were, for the first time, established between the structural and Fourier-transform infrared (FTIR) spectroscopic features for a set of kaolinite samples which differed in terms of their relative amounts of coexisting high- and low-ordered phases. For this purpose, a representative collection of kaolinites differing in origin, particle size, and degree of disorder was studied by powder X-ray diffraction (XRD) and FTIR spectroscopy. Modeling of the experimental XRD patterns based on the orthogonal layer unit cell having a mirror plane showed each sample to be a mixture of nearly defect-free high-ordered (HOK) and low-ordered (LOK) kaolinite phases, with HOK varying from 86 to 4%. The wavenumbers, heights, areas, and full widths at half-maximum (FWHM) were determined for the OH-stretching bands at ~3697 (ν1), ~3670 (ν2), ~3652 (ν3), and 3620 cm–1 (ν4) by decomposition and fitting of the FTIR spectra. The FWHM(ν1)/FWHM(ν4) and FWHM(ν3)/FWHM(ν2) values were related linearly to the HOK content, which may be associated with the in-phase and out-of-phase character of the corresponding pairs of vibrations, respectively. A novel interpretation was suggested for the variations in the relative integrated intensities of the OH bands with the amount of the HOK phase. The intensity distribution of the ν2 and ν3 bands is controlled by the triclinic structure symmetry in the defect-free kaolinite and the mirror symmetry of the layers in low-ordered structures, in agreement with the observed evolution of the corresponding band intensities. The ν1 and ν2 band positions for the low-ordered samples are within the wavenumber range for the high-ordered samples. In contrast, the ν3 and ν4 band positions for the low-ordered samples are shifted toward higher wavenumbers, indicating that some of the low-ordered kaolinites should contain dickite-like structural fragments distributed among kaolinite layers.

Identification and composition of carbonate minerals of the calcite structure by Raman and infrared spectroscopies using portable devices

A portable Raman device with a 532 nm excitation laser and a portable infrared spectrometer with ATR (Attenuated Total Reflection) mode were used to analyse the spectral features associated with the identification and compositional variation of Ca-Mg-Fe-Mn natural carbonate minerals with a calcite structure (calcite, ankerite, dolomite, siderite, rhodochrosite, and magnesite). A systematic study of the variations of the peak positions with various compositional ratios was carried out. Most of the band positions were shifted to lower wavenumbers with increasing ionic radius or atomic mass of the divalent cations but the band of the translational lattice (T) mode in Raman and the symmetric bending (ν4) band in the mid-infrared were the most sensitive. Therefore, the elemental variation of the Ca-Mg-Fe-Mn ratio in this carbonate series can be estimated from Raman and infrared band positions from spectra acquired with portable spectrometers.

Measurements and theoretical estimation of N2-broadening and -shifting coefficients of the water vapor spectral lines in the 22,330-22,590 cm−1 region

The water vapor line broadening and shifting coefficients for 36 strongest water vapor lines in the 22,330-22,590 cm−1 spectral region (6ν1+ν3 and 7ν1 bands) induced by nitrogen pressure have been measured with a spectral resolution of 0.1 cm−1 at room temperature by a Fourier transform spectrometer using a high luminance LED source. A high signal-to-noise ratio (S/N ≈ 10 000) allows one to analyze the lines with intensities from 1.25 × 10−25 to 1.15 × 10−26 cm/molecule. The N2-broadening and shifting coefficients have been calculated by a semi-empirical approach that estimates the line profiles based on anharmonic wave functions; this method explicitly takes into account all scattering channels induced by collisions.

Line-strengths, collisional coefficients and narrowing parameters in the ν3 band of methane: H2, He, N2, O2, Ar and CO2 collider effects

The ν3 fundamental absorption band of methane (12CH4) dominates the 3.3–3.4 μm infrared spectral window and has been extensively used for atmospheric, planetary and astrophysical investigations. Spectroscopic data, such as line positions, line-strengths and foreign-collisional coefficients, are needed to analyze the infrared spectra of planetary atmospheres for the understanding of relevant physical chemistry. In this study, high-resolution infrared spectra of 12CH4 belonging to the ν3 fundamental vibrational band are recorded over 2884–2969 cm−1 with a difference–frequency–generation (DFG) laser having a linewidth of Δν ≈ 0.0002 cm−1. Line-strengths as well as H2-, He-, N2-, O2-, Ar- and CO2- broadening coefficients are determined for 49 methane transitions at room temperature. Data are retrieved using Voigt and Galatry profiles to compute the measured line shape of each individual transition at various pressures. Narrowing coefficients due to Dicke effect are also determined. The new data extend and supplement previous measurements over the target spectral region (2884–2969 cm−1) where very fewer studies are reported. In particular, the present work is the first known complete determination of broadening data and narrowing parameters at high rotational quantum numbers of the P-branch of the ν3-CH4 band.

High resolution FTIR study of the ν5, ν6, and ν9 fundamental bands of CH2D37Cl

The first high-resolution infrared spectra of CH2D37Cl have been investigated in the region 650–1100 cm−1 where the lowest fundamental bands ν5 (826.2626 cm−1), ν6 (708.4307 cm−1), and ν9 (986.3405 cm−1) occur. These vibrations perturb each other by different weak interactions and the v5 = 1 and v6 = 1 states were treated according to a model which accounts for a c-type Coriolis resonance. The spectral analysis resulted in the identification of 1664, 2550 and 2657 ro-vibrational transitions for ν5, ν6, and ν9 bands respectively, and to the determination of accurate spectroscopic parameters by using the Watson’s A-reduction Hamiltonian in the Ir representation. The simulations of the ro-vibrational structure of the ν5, ν6, and ν9 bands performed in different spectral regions adequately reproduce the experimental data.

The closure temperature(s) of zircon Raman dating

Abstract. Zircon Raman dating based on irradiation damage is a debated concept but not an established geo-/thermochronological method. One issue is the temperature range of radiation-damage annealing over geological timescales. We conducted isochronal and isothermal annealing experiments on radiation-damaged zircons between 500 and 1000 ∘C for durations between 10 min and 5 d to describe the annealing kinetics. We measured the widths (Γ) and positions (ω) of the ν1(SiO4), ν2(SiO4), and ν3(SiO4) internal Raman bands, and the external rotation Raman band at ∼974, 438, 1008, and 356 cm−1 after each annealing step. We fitted a Johnson–Mehl–Avrami–Kolmogorov and a distributed activation energy model to the fractional annealing data, calculated from the widths of the ν2(SiO4), ν3(SiO4), and external rotation bands. From the kinetic models, we determined closure temperatures Tc for damage accumulation for each Raman band. Tc ranges from 330 to 370 ∘C for the internal ν2(SiO4) and ν3(SiO4) bands; the external rotation band is more sensitive to thermal annealing (Tc∼260 to 310 ∘C). Our estimates are in general agreement with previous ones, but more geological evidence is needed to validate the results. The Tc difference for the different Raman bands offers the prospect of a multi-closure-temperature zircon Raman thermochronometer.