Infrared Absorption Lines Research Articles

Unraveling the Structure-Spectrum Relationship of Yeast Phenylalanine Transfer RNA: Insights from Theoretical Modeling of Infrared Spectroscopy.

Yeast phenylalanine tRNA (tRNAphe) is a paradigmatic model in structural biology. In this work, we combine molecular dynamics simulations and spectroscopy modeling to establish a direct link between its structure, conformational dynamics, and infrared (IR) spectra. Employing recently developed vibrational frequency maps and coupling models, we apply a mixed quantum/classical treatment of the line shape theory to simulate the IR spectra of tRNAphe in the 1600-1800 cm-1 region across its folded and unfolded conformations and under varying concentrations of Mg2+ ions. The predicted IR spectra of folded and unfolded tRNAphe are in good agreement with experimental measurements, validating our theoretical framework. We then elucidate how the characteristic L-shaped tertiary structure of the tRNA and its modulation in response to diverse chemical environments give rise to distinct IR absorption peaks and line shapes. These calculations effectively bridge IR spectroscopy experiments and atomistic molecular simulations, unraveling the molecular origins of the observed IR spectra of tRNAphe. This work presents a robust theoretical protocol for modeling the IR spectroscopy of nucleic acids, which will facilitate its application as a sensitive probe for detecting the fluctuating secondary and tertiary structures of these essential biological macromolecules.

Fabrication of freestanding photonic devices combining polymer films with microfabrication techniques and 3D printing.

We report a technological concept for freestanding photonic elements based on metamaterials fabricated on polymer films by clean-room processes and framed using 3D printing. A spin-coated cyclic olefin copolymer (TOPAS) of variable thickness down to one micrometer was used as the substrate onto which metamaterials were fabricated using optical lithography. We demonstrate the possibility of applying a second TOPAS layer to protect the device or to allow for stacking another metamaterial layer. To obtain freestanding elements, frames were 3D printed directly on top of the metamaterial before lift-off from the carrier wafer. This ensured maintaining the flatness of the elements. Both the cleanroom process and the 3D printing enabled the design and manufacturing of elements in different sizes and shapes, e.g., to adapt to specific experimental set-ups and holder geometries or to be compatible with standard optical mounts. While TOPAS is transparent for wavelengths from UV to the far infrared, except for a few infrared absorption lines, we illustrate the concept with the simulation and manufacturing of THz band-pass filters. The performance of the fabricated filters was assessed using THz time-domain spectroscopy. The process is scalable to other wavelength ranges and has the potential for upscaling in manufacturing.

Infrared Spectra of (Z)- and (E)-•CH2C(CH3)CHI Radicals Produced upon Photodissociation of (Z)- and (E)-(CH2I)(CH3)C═CHI in Solid para-Hydrogen.

Ozonolysis of isoprene is important in atmospheric chemistry because of the abundant emission of isoprene. This process produces the Criegee intermediates CH2OO, methyl vinyl ketone oxide (MVKO, C2H3C(CH3)OO), and methacrolein oxide (MACRO, CH2C(CH3)CHOO). Gaseous MACRO was recently produced and identified in laboratories after photolysis of a mixture of 1,3-diiodo-2-methyl-prop-1-ene [(CH2I)(CH3)C═CHI] and O2, but the conformation-dependent formation mechanism remains unexplored. We report conformation-distinct IR spectra of (E)- and (Z)-(CH2I)(CH3)C═CHI isolated in solid p-H2. Upon irradiation near 300 nm of (E)- and (Z)-(CH2I)(CH3)C═CHI in solid p-H2 at 3.3 K, 3-iodo-2-methyl-prop-1-en-3-yl [•CH2C(CH3)CHI] radicals were characterized, with intense infrared absorption lines at 2991.3, 1458.7, 1434.7, 1317.4, 1190.4, 786.3, 677.9, and 467.2 cm-1 and additional 11 weaker ones assigned to (E)-•CH2C(CH3)CHI and intense lines at 3108.5, 3076.2, 3028.5, 2970.0, 1174.2, 796.0, 683.6, and 609.5 cm-1 and additional 7 weaker ones to (Z)-•CH2C(CH3)CHI. The assignments were derived according to the behaviors of secondary photolysis at 495 and 460 nm and a comparison of the vibrational wavenumbers and IR intensities of the observed lines with those calculated with the B2PLYP-D3/aug-cc-pVTZ-pp method. These observations confirm that only the allylic C-I bond, not the vinylic one, was photodissociated at 290 nm, and in solid p-H2, the excess energy upon photolysis induced no conformational change. When O2 was present in the matrix, several intense lines at 1147.5, 1025.7, 914.4, and 728.7 cm-1, and 4 weaker ones were tentatively assigned to the adduct CH2C(CH3)CHIOO; the assignments were supported by 18O2 isotopic experiments. Unlike in the gaseous phase, the remaining C-I bond of this adduct could not break to form MACRO because of the efficient quenching in a low-temperature matrix.

Importance of source structure on complex organics emission

Context. The hot molecular core phase of massive star formation shows emission from complex organic molecules. However, these species are only detected toward a fraction of high-mass protostars. In particular, there is a spread of ~2 orders of magnitude in methanol emission intensity from high-mass protostars. Aims. The goal of this work is to answer the question of whether high-mass disks can explain the lack of methanol emission from some massive protostellar systems. Methods. We considered an envelope-only and an envelope-plus-disk model and used the code RADMC-3D to calculate the methanol emission. High and low millimeter (mm) opacity dust (representing large and small dust distributions) were considered for both models separately, and the methanol abundance was parameterized. Viscous heating was included due to the high accretion rates of these objects in the disk. Results. In contrast with low-mass protostars, the presence of a disk does not significantly affect the temperature structure and methanol emission. The shadowing effect of the disk is not as important for high-mass objects, and the disk midplane is hot because of viscous heating, which is effective due to the high accretion rates. The methanol emission is lower for models with high mm opacity dust because the dust attenuation blocks the emission in the envelope and hides it in the disk through continuum oversubtraction, but the disk needs to be large for this to become effective. A minimum disk size of ~2000–2500 au is needed (at L = 104 L⊙) with high mm opacity dust for drop of a factor of about one order of magnitude in the methanol emission compared with the envelope-only models with low mm opacity dust. Consistent with observations of infrared absorption lines toward high-mass protostars, we find a vertical temperature inversion, that is, higher temperatures in the disk midplane than the disk surface, at radii ≲50 au for models with L = 104 L⊙ and high mm opacity dust as long as the envelope mass is ≳550 M⊙ (Ṁ = 3.6 × 10−3 M⊙ yr−1). Conclusions. The large observed scatter in methanol emission from massive protostars can be mostly explained toward lower-luminosity objects (~103 L⊙) with the envelope-plus-disk models including low and high mm opacity dust. The methanol emission variation toward sources with high luminosities (≳104 L⊙) cannot be explained by models with or without a disk with a relatively high gas-phase abundance of methanol. However, the luminosity-to-mass ratios of these objects suggest that they might be associated with hypercompact or ultracompact HII regions. Therefore, the low methanol emission toward the high-luminosity sources can be explained by them hosting an HII region in which methanol is absent.

Aluminum Bowties for Plasmonic‐Enhanced Infrared Sensing

AbstractPlasmonic nanoantennas have earned outstanding credits for their powerful ability to couple light from free‐space into sub‐wavelength‐sized structures and to enhance the electric field confinement. One of the most appealing plasmonic applications is biosensing: to detect and identify many bio‐information of a molecule in a single test. Consequently, surface enhanced spectroscopy in a broad infrared (IR) range is required. In this article, a barcode‐like nanostructured surface of a metal‐insulator‐metal (MIM) platform serves as optical transducer with tunable localized surface resonances (LSPR). The conception, fabrication, and optical characterization of periodic arrays of aluminum bowties (Al‐BT) within a MIM structure compatible with Si‐technology are reported. LSPR positions are extended by controlling the side length of the tip‐to‐tip facing triangles. The reflectance measurements correlate extremely well to numerical simulations. The simulated electrical field confinement provides up to 103 of intensity relying on the tip‐to‐tip nanogap value. Surface‐enhanced infrared absorption (SEIRA) gives simultaneously spectral information on both far‐field behavior and near‐field enhancement of several vibrational lines of our trial molecule (vanillin) achieved with the barcode‐like Al‐BT. The analysis of Fano‐like profiles is concluded with SEIRA enhancement factors higher than 107 for frequency tuning ratios below 1 between the far‐field plasmonic resonances and the selected vanillin IR absorption lines.

Oxygen in antimony triselenide: An IR absorption study

Oxygen in single crystalline antimony triselenide (Sb2Se3) is addressed by infrared (IR) absorption spectroscopy. Measurements conducted on Sb2Se3 samples doped—during growth, post-growth annealing in the O2 ambient, or by O ion implantation—with 16O reveal an IR absorption line at 527 cm−1 (10 K). Substitution of 16O by 18O “red”-shifts the signal down to 500 cm−1 based on which the line is assigned to a local vibrational mode of an isolated oxygen defect. Annealing of O-enriched samples in hydrogen atmosphere at temperatures above 380 °C results in the suppression of the 527-cm−1 line and concurrent appearance of the signals due to hydroxyl groups, suggesting formation of oxygen-hydrogen complexes. The configuration of the 527-cm−1 oxygen center is discussed.

SO 4 in Cadmium Chalcogenides: CdSe versus CdTe

A study combining infrared (IR) absorption spectroscopy and first-principles theory is presented for a sulfur–oxygen complex in CdSe characterized by IR absorption lines located at 1094, 1107, and 1126 cm−1 (10 K). The properties of the center are compared to a similar species occurring in CdTe that gives rise to two absorption lines at 1097 and 1108 cm−1 (10 K). Temperature- and polarization-sensitive measurements performed on 18O-enriched samples reveal that for both materials the IR absorption lines are due to split ν 3 stretch vibrations of a distorted sulfate ( SO 4 ) tetrahedron, whereby the local point group of the SO 4 complex is reduced to C s and C 3 v in hexagonal CdSe and cubic CdTe, respectively. Measurements on the vibrational spectrum of the sulfate species in the spectral range of symmetric stretch ( ν 1 ), bend ( ν 4 ), and combination modes ( ν 1 + ν 3 ) are presented. The cation vacancy V C d is discussed as a likely site occupied by SO 4 in CdSe.

The Central 300 pc of the Galaxy Probed by Infrared Spectra of H3 + and CO. III. Locations of Sgr B2 and Star Iota

Abstract Using a simple relation between the radial expansion velocity of diffuse gas in the Central Molecular Zone (CMZ) of the Galaxy and its distance from Sgr A* we estimate the physical depths within the CMZ of Star ι (2MASS J17470898-2829561) and two Sgr B2 far-infrared continuum sources with respect to the location of Sgr A*. To do this we use velocity profiles of infrared absorption lines of H 3 + and of far-infrared absorption lines of H2O+, OH+, and 13CH+. The distances to Star ι and to the Sgr B2 sources are found to be ∼90 pc greater than the distance to Sgr A*. Our conclusion that Sgr B2 lies toward the rear of the CMZ is contrary to most previous models in which it has been placed shallower than Sgr A*.

Absorptive laser threshold magnetometry: combining visible diamond Raman lasers and nitrogen-vacancy centres

We propose a high-sensitivity magnetometry scheme based on a diamond Raman laser with visible pump absorption by an ensemble of coherently microwave driven negatively charged nitrogen-vacancy centres (NV−) in the same diamond crystal. The NV− centres’ absorption and emission are spin-dependent. We show how the varying absorption of the NV− centres changes the Raman laser output. A shift in the diamond Raman laser threshold and output occurs with the external magnetic field and microwave driving. We develop a theoretical framework with steady-state solutions to describe the effects of coherently driven NV− centres including the charge state switching between NV− and its neutral charge state NV0 in a diamond Raman laser. We discuss that such a laser working at the threshold can be employed for magnetic field sensing. In contrast to previous studies on NV− magnetometry with visible laser absorption, the laser threshold magnetometry method is expected to have low technical noise, due to low background light in the measurement signal. For magnetic-field sensing, we project a shot-noise limited DC sensitivity of a few pT in a well-calibrated cavity with realistic parameters. This sensor employs the broad visible absorption of NV− centres and unlike previous laser threshold magnetometry proposals it does not rely on active NV− centre lasing or an infrared laser medium at the specific wavelength of the NV− centre’s infrared absorption line.

Photoacoustic spectroscopy: Trace CO detection by using 10 mW near-infrared laser and cantilever beam

Sulfur hexafluoride (SF6) is commonly used in gas insulated switchgears (GIS) as an insulating medium. When local overheating or partial discharge occurs in GIS, SF6 may be decomposed into various products including CO. In this paper, based on the photoacoustic (PA) effect of gas molecules, the infrared absorption line at 6380.318 cm−1 was chosen as the target line. An infrared laser with a center wavelength of 1567 nm was chosen as the light source, and a cantilever enhanced PA detector was used as the sensor; then, the experimental platform was constructed. The influence of the temperature and pressure on the infrared absorption coefficient of CO was analyzed. The relationship of the PA signal and the CO concentration under the background of SF6 and N2 were obtained. The results show that the temperature has a great influence on the CO absorption coefficient while the influence of pressure is negligible, and the temperature influential coefficient is about 5.0 × 10−6 cm−1/°C. The detection system has the highest signal-to-noise ratio when the frequency of the chopper is 40 Hz. Under N2 and SF6 background gases, there is a good linear relationship between CO concentration and pure PA signals. The minimum detection limit of CO in the background of N2 is 3.63 ppm, while it is 9.88 ppm in SF6. The different kinds of the background gases can influence the PA signals. The PA signals decrease with the increase of the temperature of the gas cell, and they also decrease with the increase of the pressure.

Infrared Spectra of (Z)- and (E)-•C2H3C(CH3)I Radicals Produced upon Photodissociation of (Z)- and (E)-(CH2I)HC═C(CH3)I in Solid para-Hydrogen.

Ozonolysis of isoprene to produce Criegee intermediates such as methyl vinyl ketone oxide (MVKO), C2H3C(CH3)OO, is an important process in atmospheric chemistry. MVKO was recently produced and identified in laboratories after photolysis of a gaseous mixture of 1,3-diiodo-but-2-ene, (CH2I)HC═C(CH3)I, and O2, but the mechanism of its formation remains unexplored. We synthesized pure (Z)- and (E)-1,3-diiodo-but-2-ene and measured their distinct IR spectra. Upon irradiation at 280 nm of (Z)- and (E)-1,3-diiodo-but-2-ene in solid p-H2 at 3.3 K, the fission of the terminal C-I bond yields (Z)- and (E)-3-iodo-but-2-en-1-yl [•C2H3C(CH3)I] radicals, respectively. These radicals were characterized with infrared absorption lines at 2962.4, 1423.8, 1265.3, 1120.9/1127.0, 921.4/922.3, and 792.5/791.7 cm-1, and 16 additional weaker lines for (Z)-•C2H3C(CH3)I and 1405.2, 1208.2, 1106.0/1103.9, 934.2/933.4, and 785.1/784.9 cm-1 and five additional weaker ones for (E)-•C2H3C(CH3)I. The assignments were derived according to behavior on secondary photolysis and comparison of the vibrational wavenumbers and the IR intensities of observed lines with those calculated with the B2PLYP-D3/aug-cc-pVTZ-pp method. These observations confirmed that only the terminal I atom, not the central one, was photodissociated at 280 nm and, in solid p-H2, the excess energy after photodissociation induced no change in conformation. These new spectra of •C2H3C(CH3)I radicals can provide valuable information for the understanding of the mechanism of formation of Criegee intermediate MVKO from the source reaction of photolysis of (CH2I)HC═C(CH3)I in O2 in the laboratory.

Reaction of CH2Cl radical with O2 in solid para-hydrogen: Infrared spectrum of gauche-CH2ClOO radical

Irradiation of a para-hydrogen (p-H2) matrix containing chloroiodomethane (CH2ClI) and O2 at 3.3 K with light at 290 nm yielded infrared absorption lines at 750.1/745.6, 891.7, 1004.6, 1090.7, 1241.3, 1315.6, 1427.8, and 2988.7 cm−1, which are assigned to the gauche-chloromethylperoxy radical (gauche-CH2ClOO). Further irradiation of the matrix at 240 nm selectively diminished these features. The assignments are based on the photolytic behavior and comparisons of the observed vibrational wavenumbers and IR intensities with those predicted with the B3LYP/aug-cc-pVTZ method. The irradiation of CH2ClOO at 240 nm was found to induce cleavage of the O–O bond to produce CH2ClO, but not cleavage of the C–Cl bond to produce the Criegee intermediate CH2OO.

H2-induced pressure broadening and pressure shift in the P-branch of the ν3 band of CH4 from 300 to 655 K

For accurate modelling of observations of exoplanet atmospheres, quantification of the pressure broadening of infrared absorption lines for and by a variety of gases at elevated temperatures is needed. High-resolution high-temperature H2-pressure-broadened spectra are recorded for the CH4ν3-band P-branch. Measured linewidths for 143 transitions between 2840 and 3000 cm−1 with temperature and pressures ranging between 300 and 655 K, and 10 and 933 Torr, respectively, were used to find rotation- and tetrahedral-symmetry-dependent coefficients for pressure and temperature broadening and pressure-induced lineshifts. The new pressure-broadening data will be useful in radiative-transfer models for retrieving the properties of observed expolanet atmospheres.

Formation and Dissociation of N3 in Icy N2 with Far-ultraviolet Light

Abstract During photoexcitation of icy N2 at 121.6 nm from a synchrotron source, emission lines in the vibronic progression of the Vegard–Kaplan system, A , for N2 were concurrently observed in the wavelength range 210–430 nm; emission lines of N (2P → 2D) and N (2D → 4S) were recorded in the wavelength range 460–1100 nm. After irradiation of icy N2 at 121.6 nm, the characteristic infrared absorption lines of N3 radical in vibrational mode ν 3 appeared at 1652.6 and 1657.8 cm−1. When the irradiated icy sample containing N3 radical was subsequently subjected to photolysis at 190 nm, only emission from N (2D → 4S) was concurrently recorded; the IR absorption lines of N3 vanished. The result indicates that N3 radical in icy N2 can be dissociated into the N (2D) atom and N2 ( ) molecule with light at 190 nm. Our work thus has ramifications for nitrogen transformation in cold astrophysical environments.

Electronic and Vibrational Absorption Spectra of NH2 in Solid Ne.

Irradiation of ammonia dispersed in solid neon near 4 K with tunable far-ultraviolet light from a synchrotron yielded amidogen, NH2, and imidogen, NH, radicals as products. The electronic absorption spectra of amidogen radicals in isotopic variants NH2, NHD, and ND2 were recorded in the visible and near-ultraviolet regions after photolysis of NH3 and ND3. The infrared absorption lines of NH2 associated with vibration-rotational levels of vibrational modes ν1 at 3234.3 (00,0–10,1), 3244.9 (00,0–11,1), and 3249.3 cm–1 (00,0–11,0), and ν2 at 1498.7 (10,1–11,1), 1509.5 (11,0–10,1), 1516.5 (00,0–10,1), 1528.6 (00,0–11,1), and 1533.7 cm–1 (00,0–11,0) were unambiguously identified according to the results of experiments with deuterium isotopes. The 00,0–00,0 lines of ν1 and ν2 for NH2 were derived to be at 3213.5 and 1494.6 cm–1 in solid neon.

Infrared laser threshold magnetometry with a NV doped diamond intracavity etalon.

We propose a hybrid laser system consisting of a semiconductor external cavity laser associated to an intra-cavity diamond etalon doped with nitrogen-vacancy color centers. We consider laser emission tuned to the infrared absorption line that is enhanced under the magnetic field dependent nitrogen-vacancy electron spin resonance and show that this architecture leads to a compact solid-state magnetometer that can be operated at room-temperature. The sensitivity to the magnetic field limited by the photonshot-noise of the output laser beam is estimated to be less than 1pT/Hz. Unlike usual NV center infrared magnetometry, this method would not require an external frequency stabilized laser. Since the proposed system relies on the competition between the laser threshold and an intracavity absorption, such laser-based optical sensor could be easily adapted to a broad variety of sensing applications based on absorption spectroscopy.

Re-analysis of the high-resolution FTIR spectrum of the [formula omitted] band of 13C2HD3 in the 810–1010 cm−1 region: Coriolis interactions with the [formula omitted] and [formula omitted] bands

The spectrum of the C-type ν8 band of 13C2HD3, in the region of 810 to 1010 cm−1, was recorded using a Fourier transform infrared (FTIR) spectrometer, at an unapodized resolution of 0.0019 cm−1. Improved rovibrational constants of the v8=1 state up to five quartic terms were derived from a fit of 1433 assigned unperturbed infrared transitions using Watson's A-reduced Hamiltonian in the Ir representation. For the first time, Coriolis interactions between the v8=1, v6=1 and v3=1 states were studied. A total of 828 perturbed infrared absorption lines, together with the unperturbed infrared transitions, were fitted to obtain a precise set of three rotational constants for the v6=1 state, band centers for the ν6 and ν3 bands, and two a- and b-Coriolis resonance parameters. The fit of an expanded set of ground state combination-differences derived from a larger number of perturbed and unperturbed infrared measurements in this work also yielded rotational and quartic centrifugal distortion constants of the ground state of 13C2HD3 with improved precision, with an rms deviation of 0.00040 cm−1. The experimentally-derived rotational constants of the ground and v8=1 states compared favourably with those from anharmonic calculations using the MP2/cc-pVQZ and B3LYP/cc-pVQZ levels of theory.

Infrared spectra of 3-hydroxy-(1H)-pyridinium cation and 3-hydroxy-(1H)-pyridinyl radical isolated in solid para-hydrogen.

As pyridine and its derivatives are regarded as building blocks of nitrogen-containing polycyclic aromatic hydrocarbons, spectral identifications of their protonated and hydrogenated species are important. The infrared (IR) absorption spectra of the 3-hydroxy-(1H)-pyridinium cation, 3-C5H4(OH)NH+, and the 3-hydroxy-(1H)-pyridinyl radical, 3-C5H4(OH)NH, produced on electron bombardment during deposition of a mixture of 3-hydroxypyridine, 3-C5H4(OH)N, and para-H2 to form a matrix at 3.2 K were recorded. Intense IR absorption lines of trans-3-C5H4(OH)NH+ at 3594.4, 3380.0, 1610.6, 1562.2, 1319.4, 1193.8, 1167.5, and 780.4 cm-1 and eleven weaker ones decreased in intensity after the matrix was maintained in darkness for 20 h, whereas lines of trans-3-C5H4(OH)NH at 3646.2, 3493.4, 3488.7, 1546.7, 1349.6, 1244.1, 1209.1, 1177.3, 979.8, and 685.2 cm-1 and nine weaker ones increased. The intensities of lines of trans-3-C5H4(OH)NH decreased upon irradiation at 520 nm and diminished nearly completely upon irradiation at 450 nm, whereas those of trans-3-C5H4(OH)NH+ remained unchanged upon irradiation at 370, 450, and 520 nm. Observed vibrational wavenumbers and relative intensities of these species agree satisfactorily with the scaled harmonic vibrational wavenumbers and IR intensities predicted with the B3LYP/aug-cc-pVTZ method. The observed 3-C5H4(OH)NH+ cation and 3-C5H4(OH)NH radical are predicted to be the most stable species among all possible isomers by quantum-chemical calculations.

Thresholds of photolysis of O2 and of formation of O3 from O2 dispersed in solid neon.

Irradiation of O2 dispersed in solid Ne with ultraviolet light produced infrared absorption lines of O3 and emission lines from atomic O (1D2 → 3P1,2), molecular O2 (A' 3Δu → X 3Σg) and radical OH (A 2Σ+ → X 2ΠI) in the visible and near-ultraviolet regions. The threshold wavelength for the formation of O3 was determined to be 200 ± 4 nm, corresponding to energy 6.20 ± 0.12 eV, which is hence the threshold for dissociation of O2. The thresholds of emission from excited O (1D2), O2 (A' 3Δu) and OH (A 2Σ+) were all observed to be 200 ± 4 nm, the same as for the formation of O3 in this photochemical system. The results indicate that, once O3 was generated, it was readily photolyzed to produce the long-lived atom O (1D2). Further reactions of O (1D2) with O3 produced excited O2 (A' 3Δu); reaction with water yielded radical OH (A 2Σ+). These results enhance our understanding of the evolution of the transformation of oxygen and open a window for the understanding of complicated processes in the solid phase.

Diffusivity of the interstitial hydrogen shallow donor in In2O3

Hydrogen has been found to be an n-type dopant in In2O3 that gives rise to unintentional conductivity. An infrared (IR) absorption line observed at 3306 cm−1 has been assigned to the Hi+ center. Two types of experiments have been performed to determine the diffusivity of Hi+ in In2O3 from its IR absorption spectra. (i) At temperatures near 700 K, the O-H line at 3306 cm−1 has been used to determine the diffusivity of Hi+ from its in-diffusion and out-diffusion behaviors. (ii) At temperatures near 160 K, stress has been used to produce a preferential alignment of the Hi+ center that has been detected in IR absorption experiments made with polarized light. With the help of theory, the kinetics with which a stress-induced alignment can be produced yield the time constant for a single jump of the Hi+ center and also the diffusivity of Hi+ near 160 K. The combination of the diffusivity of Hi+ found near 700 K by mass-transport measurements and that found near 160 K from the time constant for a single Hi+ jump determines the diffusivity for Hi+ over eleven decades!