Aluminum Monofluoride Research Articles

Employing typicality in optimal control theory: Addressing large Hilbert spaces

Controlling the dynamics of quantum systems is a crucial task in quantum science and technology. Obtaining the driving field that transforms the quantum systems into its objective is a typical control task. This task is hard, scaling unfavorably with the size of the quantum map. To tackle this issue we employ typicality to assist in finding the control field for such transformation. To demonstrate the method we choose the control task of cooling the fine-structure states of the aluminum monofluoride molecule, at relatively high temperature. As a result high-rotational states are occupied, meaning a high effective Hilbert space. Using quantum typicality, we demonstrate that we can simulate an ensemble of states, enabling a control task addressing simultaneously many states. We employ this method to find a control field for cooling molecules with a large number of internal sates, corresponding to high initial temperatures.

First detection of AlF line emission towards M-type AGB stars

The nucleosynthesis production of fluorine (F) is still a matter of debate. Asymptotic giant branch (AGB) stars are one of the main candidates for F production. However, their contribution to the total F budget is not fully known due to the lack of observations. In this paper, we report the detection of aluminium monofluoride (AlF) line emission, one of the two main carriers of F in the gas-phase in the outflow of evolved stars, towards five nearby oxygen-rich (M-type) AGB stars. We studied the Atacama large millimetre/sub-millimetre array (ALMA) observations of AlF (v = 0, J = 4—3, 9–8, 10–9, and 15–14) and (v = 1, J = 7–6) line emission towards o Ceti, and (v = 0, J = 7–6 and 15–14) lines towards R Leo. We also report a tentative detection of AlF (v = 0, J = 7–6) line in IK Tau, (v = 0, J = 15–14) line towards R Dor, and (v = 0, J = 7–6 and J = 15–14) lines in W Hya. From spatially resolved observations, we estimated the AlF emitting region with a radius ~11R⋆ for o Ceti and ~9R⋆ for R Leo. From population diagram analysis, we report the AlF column densities of ~5.8 × 1015 cm−2 and ~3 × 1015 cm−2 for o Ceti and R Leo, respectively, within these regions. For o Ceti, we used the C18O (v = 0, J = 3–2) observations to estimate the H2 column density of the emitting region. We found a fractional abundance of fAIF/H2 ~ (2.5 ± 1.7) × 10−8. This gives a lower limit on the F budget in o Ceti and is compatible with the solar F budget fF/H2 = (5 ± 2) × 10−8. For R Leo, a fractional abundance fAIF/H2 = (1.2 ± 0.5) × 10−8 is estimated. For other sources, we cannot precisely determine the emitting region based on the available data. Assuming an emitting region with a radius of ~11R⋆ and the rotational temperatures derived for o Ceti and R Leo, we crudely approximated the AlF column density to be ~(1.2−1.5) × 1015 cm−2 in W Hya, ~(2.5−3.0) × 1014 cm−2 in R Dor, and ~(0.6−1.0) × 1016 cm−2 in IK Tau. These result in fractional abundances within a range of fAIF/H2 ~ (0.1 − 4) × 10−8 in W Hya, R Dor, and IK Tau.

Spectroscopic characterization of singlet-triplet doorway states of aluminum monofluoride.

Aluminum monofluoride (AlF) possesses highly favorable properties for laser cooling, both via the A1Π and a3Π states. Determining efficient pathways between the singlet and the triplet manifold of electronic states will be advantageous for future experiments at ultralow temperatures. The lowest rotational levels of the A1Π, v = 6 and b3Σ+, v = 5 states of AlF are nearly iso-energetic and interact via spin-orbit coupling. These levels thus have a strongly mixed spin-character and provide a singlet-triplet doorway. We here present a hyperfine resolved spectroscopic study of the A1Π, v = 6//b3Σ+, v = 5 perturbed system in a jet-cooled, pulsed molecular beam. From a fit to the observed energies of the hyperfine levels, the fine and hyperfine structure parameters of the coupled states and their relative energies as well as the spin-orbit interaction parameter are determined. The standard deviation of the fit is about 15MHz. We experimentally determine the radiative lifetimes of selected hyperfine levels by time-delayed ionization, Lamb dip spectroscopy, and accurate measurements of the transition lineshapes. The measured lifetimes range between 2 and 200ns, determined by the degree of singlet-triplet mixing for each level.

Spectroscopic characterization of the a3Π state of aluminum monofluoride.

Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All Q lines of the strong A1Π ← X1Σ+ transition around 227nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden a3Π ← X1Σ+ transition around 367nm, which has a recoil limit in the µK range. We here report on the spectroscopic characterization of the lowest rotational levels in the a3Π state of AlF for v = 0-8 using a jet-cooled, pulsed molecular beam. An accidental AC Stark shift is observed on the a3Π0, v = 4 ← X1Σ+, v = 4 band. By using time-delayed ionization for state-selective detection of the molecules in the metastable a3Π state at different points along the molecular beam, the radiative lifetime of the a3Π1, v = 0, J = 1 level is experimentally determined as τ = 1.89 ± 0.15 ms. A laser/radio frequency multiple resonance ionization scheme is employed to determine the hyperfine splittings in the a3Π1, v = 5 level. The experimentally derived hyperfine parameters are compared to the outcome of quantum chemistry calculations. A spectral line with a width of 1.27kHz is recorded between hyperfine levels in the a3Π, v = 0 state. These measurements benchmark the electronic potential of the a3Π state and yield accurate values for the photon scattering rate and for the elements of the Franck-Condon matrix of the a3Π-X1Σ+ system.

Dynamics of translational and rotational thermalization of AlF molecules via collisions with cryogenic helium

We investigated helium-mediated translational and rotational thermalization of the aluminum monofluoride (AlF) molecule at cryogenic temperatures via an ab initio potential energy surface (PES) and quantum multichannel scattering theory. Our examination of the elastic and rotationally inelastic channels revealed that helium is an efficient quencher of AlF at temperatures relevant to buffer gas cooling experiments ($\ensuremath{\sim}1$ mK to 10 K). We also showed that this conclusion is robust against possible inaccuracies of the PES.

Preparation and characterization of multifunctional piezoenergetic polyvinylidene fluoride/aluminum nanocomposite films

We prepared poly(vinylidene fluoride) (PVDF) and aluminum composite dense films using a tape caster and investigated the microstructural, thermal, and electrical properties and the combustion behavior of the films as a function of nano-aluminum (nAl) solids loading (5–30 wt. %). We found that the addition of nAl facilitates the formation of piezoelectric β and γ phases of PVDF as determined by x-ray diffraction and Fourier transform infrared spectroscopy. At higher nAl solid loadings, the lower onset temperature of the pre-ignition and decomposition reactions have been observed. Moreover, the intentionally incorporated porosity into the films slightly affected the thermal decomposition behavior. While the dielectric constant of the films increases with higher nAl content, the dielectric breakdown strength of the films decreases significantly. The critical active nAl content for the films to exhibit self-propagated reaction was determined to be between 10 and 15 wt. %. Thermochemical calculations using the NASA CEA code showed the maximum flame temperature of 1750 °C near the stoichiometric ratio (∼20 wt. %). The burning rate of the films is enhanced drastically at ambient conditions with further addition of nAl. However, the films with active nAl content over 20 wt. % showed lower flame temperatures, which is due to the reduction of hydrofluoric acid gas generation and the incomplete combustion of Al to form aluminum monofluoride (AlF), instead of aluminum fluoride (AlF3) gas. The fabrication of energetic thin films with tunable properties could enable their use in multifunctional energetic material systems.

Destruction of AlF: a quantum study of its ground-state photodissociation

ABSTRACTPhotodissociation by ultraviolet photons is the key destruction pathway for aluminium monofluoride (AlF) in the envelope of the carbon star IRC +10216 from the stellar photosphere up to the outer layers. However, there is no available photodissociation data for AlF, which hampers the prediction of the abundances of Al-bearing molecules in astrochemical models. Here, we present an ab initio study of AlF photodissociation. Potential energy curves of seven singlet states for AlF were computed by the internally contracted multireference single and double configuration-interaction method and aug-cc-pCV5Z-DK basis set, along with the transition dipole moments from excited singlet states to the ground state. State-resolved cross sections for the direct photodissociation from 36 349 ground rovibrational levels ( υ″≤120, J″≤360) to six singlet excited states were calculated by the quantum mechanical method. We found that the 21Π←X 1Σ+, 31Π←X 1Σ+, and 41Π←X 1Σ+ transitions have extremely strong absorption for lower wavelengths, especially between the Lyman and Lyman α ones. Photodissociation cross sections in local thermal equilibrium were estimated for gas temperatures from 500 to 20 000 K. Finally, the cross sections were utilized to calculate the photodissociation rates in the interstellar and blackbody radiation fields. The obtained photodissociation cross sections and rates can be used to determine the abundance of AlF in astrochemical models.

Optical cycling of AlF molecules

Aluminium monofluoride (AlF) is a promising candidate for laser cooling and trapping at high densities. We show efficient production of AlF in a bright, pulsed cryogenic buffer gas beam, and demonstrate rapid optical cycling on the Q rotational lines of the A 1Π ↔ X 1Σ+ transition. We measure the brightness of the molecular beam to be >1012 molecules per steradian per pulse in a single rotational state and present a new method to determine its velocity distribution in a single shot. The photon scattering rate of the optical cycling scheme is measured using three different methods, and is compared to theoretical predictions of the optical Bloch equations and a simplified rate equation model. Despite the large number of Zeeman sublevels (up to 216 for the Q(4) transition) involved, a high scattering rate of at least 17(2) × 106 s−1 can be sustained using a single, fixed-frequency laser without the need to modulate the polarisation. We deflect the molecu-lar beam using the radiation pressure force and measure an acceleration of 8.7(1.5) × 105 m s−2. Losses from the optical cycle due to vibrational branching to X 1Σ+, v″ = 1 are addressed efficiently with a single repump laser. Further, we investigate two other loss channels, parity mixing by stray electric fields and photo-ionisation. The upper bounds for these effects are sufficiently low to allow loading into a magneto‐optical trap.

Characterisation of the b 3Σ+, v = 0 state and its interaction with the A 1Π state in aluminium monofluoride

Recently, we determined the detailed energy level structure of the , and states of AlF that are relevant to laser cooling and trapping experiments [Truppe et al., Phys. Rev. A. 100 (5), 052513 (2019)]. Here, we investigate the state of the AlF molecule. A rotationally resolved (1 + 2)-REMPI spectrum of the band is presented and the lifetime of the state is measured to be 190(2) ns. Hyperfine-resolved, laser-induced fluorescence spectra of the and the bands are recorded to determine fine- and hyperfine structure parameters. The interaction between the and the nearby state is studied and the magnitude of the spin–orbit coupling between the two electronic states is derived using three independent methods to give a consistent value of 10(1) cm. The triplet character of the A state causes an loss from the main A−X laser cooling cycle below the 10 level.

Spectroscopic characterization of aluminum monofluoride with relevance to laser cooling and trapping

Here we report on spectroscopic measurements of the aluminum monofluoride molecule (AlF) that are relevant to laser cooling and trapping experiments. We measure the detailed energy level structure of AlF in the X$^1\Sigma^+$ electronic ground state, in the A$^1\Pi$ state, and in the metastable a$^3\Pi$ state. We determine the rotational, vibrational and electronic branching ratios from the A$^1\Pi$ state. We also study how the rotational levels split and shift in external electric and magnetic fields. We find that AlF is an excellent candidate for laser cooling on any Q-line of the A$^1\Pi$ - X$^1\Sigma^+$ transition and for trapping at high densities.

Astronomical detection of radioactive molecule 26AlF in the remnant of an ancient explosion

Decades ago, $\gamma$-ray observatories identified diffuse Galactic emission at 1.809 MeV originating from $\beta^+$ decays of an isotope of aluminium, $^{26}$Al, that has a mean-life time of 1.04 Myr. Objects responsible for the production of this radioactive isotope have never been directly identified, owing to insufficient angular resolutions and sensitivities of the $\gamma$-ray observatories. Here, we report observations of millimetre-wave rotational lines of the isotopologue of aluminium monofluoride that contains the radioactive isotope ($^{26}$AlF). The emission is observed toward CK Vul which is thought to be a remnant of a stellar merger. Our constraints on the production of $^{26}$Al combined with the estimates on the merger rate make it unlikely that objects similar to CK Vul are major producers of Galactic $^{26}$Al. However, the observation may be a stepping stone for unambiguous identification of other Galactic sources of $^{26}$Al. Moreover, a high content of $^{26}$Al in the remnant indicates that prior to the merger, the CK Vul system contained at least one solar-mass star that evolved to the red giant branch.

Thermodynamic Analysis of a New Gas-Phase Method of Obtaining High-Purity Aluminum Nitride

Ultradispersed high-purity aluminum nitride powder was obtained at the Physico-Technological Institute on a unique experimental-industrial unit by a gas-phase method. The powder was obtained through the formation of aluminum monofluoride. However, there has been very little thermodynamic analysis of the interactions of the materials in the reaction zone and in the charge. This study gives special attention to the selection of sintering additives and their effect on the removal of undesirable oxygen impurities during the synthesis of aluminum nitride. The mix that was obtained for sintering can be used for the energy-efficient single-stage production of aluminum-nitride finished products having excellent thermal conductivity.

Determination of Fluorine by Molecular Absorption Spectrometry of AlF Using a High-Resolution Continuum Source Spectrometer and a C<sub>2</sub>H<sub>2</sub>/N<sub>2</sub>O Flame

The molecular absorption of the diatomic AlF molecule in the C2H2/N2O flame was studied using a highresolution continuum source flame atomic absorption spectrometer. AlF has a structured absorption spectrum in the range of 227.30 nm and 227.80 nm. From this band system, the remarkably narrow absorption band at 227.66 nm proved to be the optimum for analytical purposes. The signal intensity was studied as a function of the C2H2 : N2O ratio, the aspiration flow, and the aluminum concentration added to the analytical solution to generate the AlF molecules in the flame. The AlF molecule formation is significantly affected by the bonding state of the fluorine source used. Compared to ionic bound fluorine, organic bound fluorine leads to a markedly less sensitive molecular absorbance of AlF. Furthermore, several ions, such as Na+, K+ and NH4+ +, and acids, such as HCl, CH3COOH, and HNO3, affect the AlF signal intensity severely. It has to be concluded that the determination of fluorine by AlF F MAS only leads to reliable analytical results in simple matrices. Keywords: Aluminum monofluoride (AlF), fluorine determination, high resolution continuum source absorption spectrometry, molecular absorption spectrometry (MAS), non-spectral interference.

Ultraviolet absorption spectroscopy in optically dense fireballs using broadband second-harmonic generation of a pulsed modeless dye laser.

Broadband frequency doubling of a modeless dye laser pulse is used to enable single-shot absorption spectroscopy in the ultraviolet for optically dense, energetic-materials fireball applications. Band widths of approximately 1-3 nm are generated in the 226 and 268 nm regions using a doubling crystal. Strong focusing of the fundamental beam onto the crystal is found to be sufficient to achieve 1-5% conversion efficiency with a pulse intensity sufficient to saturate the array detector even after 75% attenuation through the fireball. The technique is demonstrated with nitric oxide (NO) absorption in a gas cell and is then used to perform the first detection and temperature fitting of aluminum monofluoride (AlF) and magnesium monofluoride (MgF) in a fireball environment.

The formation of AlF by radiative association

The formation of the aluminium monofluoride molecule AlF by radiative association of the Al and F atoms is estimated. The radiative association of Al(2P) and F(2P) atoms is found to be dominated by the approach along the A1Π potential energy curve accompanied by spontaneous emission into the X1Σ+ ground state of the AlF. For temperatures ranging from 300 to 14 000 K, the rate coefficients are found to vary from 1.35 × 10−17 to 9.31 × 10−16 cm3 s−1, respectively. These values indicate that only a small amount of AlF molecules can be formed by radiative association in the inner envelope of carbon-rich stars and other hostile environments.

Method development for the determination of fluorine in toothpaste via molecular absorption of aluminum mono fluoride using a high-resolution continuum source nitrous oxide/acetylene flame atomic absorption spectrophotometer

Fluorine was determined via the rotational molecular absorption line of aluminum mono fluoride (AlF) generated in C2H2/N2O flame at 227.4613nm using a high-resolution continuum source flame atomic absorption spectrophotometer (HR-CS-FAAS). The effects of AlF wavelength, burner height, fuel rate (C2H2/N2O) and amount of Al on the accuracy, precision and sensitivity were investigated and optimized. The Al–F absorption band at 227.4613nm was found to be the most suitable analytical line with respect to sensitivity and spectral interferences. Maximum sensitivity and a good linearity were obtained in acetylene-nitrous oxide flame at a flow rate of 210Lh−1 and a burner height of 8mm using 3000mgL−1 of Al for 10–1000mgL−1of F. The accuracy and precision of the method were tested by analyzing spiked samples and waste water certified reference material. The results were in good agreement with the certified and spiked amounts as well as the precision of several days during this study was satisfactory (RSD<10%). The limit of detection and characteristic concentration of the method were 5.5mgL−1 and 72.8mgL−1, respectively. Finally, the fluorine concentrations in several toothpaste samples were determined. The results found and given by the producers were not significantly different. The method was simple, fast, accurate and sensitive.

Rotational excitation of aluminium monofluoride (AlF) by He atom at low temperature

We report on the calculation of collision induced rotational excitation cross sections and rate coefficients of AlF by He atom at low temperature. These quantities were obtained by first computing the interaction potential energy surface (PES) of the AlF(X 1Σ+)-He(1S) van der Waals complex at the ab initio Coupled Cluster with Single and Double and perturbative Triple excitations [CCSD(T)] level of theory. The aug-cc-pVQZ Gaussian basis, to which was added a set of bond functions, was used for that purpose. The calculations account for basis set superposition errors (BSSE). The interaction potential presents a minimum of ∼24 cm−1 below the AlF-He dissociation limit. The PES was fitted on a basis of Legendre polynomial functions to allow for the calculation of cross sections in the close-coupling (CC) approach. By averaging these cross sections over a Maxwell-Boltzmann velocity distribution, rate coefficients were inferred at low temperatures (T≤300 K). From our computations, a propensity towards ΔJ=1 transitions is observed.

A new approach for fluorine determination by solid sampling graphite furnace molecular absorption spectrometry

This work deals with the determination of fluorine by solid sampling graphite furnace molecular absorption spectrometry. The molecular absorbance of aluminum monofluoride (AlF), which is produced in the vapor phase in the presence of Al 3+, is measured at 227.5 nm, a non-resonant platinum line. A conventional graphite furnace program has been used with pyrolysis and vaporization temperatures of 800 and 2300 °C, respectively. Solutions of Ba 2+ and Al 3+ have been used to avoid fluorine losses during the pyrolysis stage and to produce AlF in the vaporization stage, respectively. Certified coal and alumina samples were analyzed using aqueous standards for calibration. The agreement between the found concentration and the certified value, or the value obtained by another method ranged from 92 to 105%, with a relative standard deviation less than 8.5%. The limit of detection and the characteristic mass was 0.17 μg g − 1 and 205 pg, respectively.

A Bulky Chelating Diamidoaluminum Monohydride − Synthesis, Structure and Reactions with Me3SnF and Heavy Group 16 Elements

AbstractThe bulky chelating diamidoaluminum monohydride [ArN(CH2)3NAr]AlH(NMe3) (Ar = 2,6‐iPr2C6H3; 1) was prepared in excellent yield from the reaction of the diamine ArNH(CH2)3HNAr with a small excess of AlH3·NMe3 in toluene. Subsequent fluorination of 1 with Me3SnF resulted in the formation of the aluminum monofluoride [ArN(CH2)3NAr]AlF(NMe3) (2). Reaction of 1 with elemental E (E = S, Se and Te) proceeded in toluene with heating to yield the aluminum chalcogenides {[ArNH(CH2)3NAr]Al(μ‐E)}2 [E = S (3), Se (4), and Te (5)]. The structures of complexes 1, 2 and 4 have been determined by X‐ray diffraction analyses. Compounds 1 and 2 are well‐separated monomers with a central aluminum atom in a tetrahedral environment. The diamide ligand [ArN(CH2)3NAr]2− chelates the Al atom to form a distorted six‐membered AlN2C3 ring which features a boat conformation for 1 and a flattened chair conformation for 2. Compound 4, however, is a dimer with a central Al2Se2 core bearing an ideal four‐membered planar ring and two six‐membered AlN2C3 rings, both displaying a boat conformation. The latter two rings are arranged perpendicularly to the Al2Se2 core in a trans configuration. The IR spectra and 1H NMR spectroscopic data of compounds 3−5 suggest that the migration of the hydrogen from selenium to one of the nitrogens at the diamide ligand is involved in the course of the reaction. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

Direct Determination of Individual Organic Fluorine Compounds by Aluminum Monofluoride Molecular Absorption Spectrometry

Abstract Recovery of organic fluorine by direct aluminum monofluoride molecular absorption spectrophotometry, following injection of samples into the graphite furnace and use of sodium fluoride standards, varies from 0 to 100% from compound to compound depending on the compound's volatility and the mechanism of thermal decomposition. This problem has now been overcome by employing standards made from the very same fluorochemical that is present in the sample. This approach is applicable to samples containing only 1 known fluorochemical. Some industrial applications of this technique that meet the needs of quality control, industrial hygiene policies, and certain U.S. Food and Drug Administration regulations are described.