Construction and Demonstration of a 6–18 GHz Microwave Three-Wave Mixing Experiment using Multiple Synchronized Arbitrary Waveform Generators

This manuscript details the construction and demonstration of the first known microwave three-wave mixing (M3WM) experiment utilizing multiple arbitrary waveform generators (AWGs) completely operable in the 6–18 GHz frequency range for use in chirality determination and quantification. Many M3WM techniques, which involve two orthogonal, subsequent Rabi π/2 and π microwave pulses, suffer from flexibility in pulse types and timings as well as frequency due to most instruments only using one, one-channel AWG and the M3WM probability decreasing with an increasing quantum number, J. In this work, we presented an M3WM instrument that allows that flexibility by introducing multiple, synchronized AWGs and adheres to the high probability transition loop pathways in carvone. The functionality and reliability of the instrument were demonstrated using a series of experiments and mixtures of the R and S enantiomers and determined to be of similar accuracy to other reported M3WM setups with the additional benefit of flexibility in pulsing schemes

The Covalent Interaction between Dihydrogen and Gold: a Rotational Spectroscopic Study of H₂-AuCl

The pure rotational transitions of H2-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both 35Cl and 37Cl isotopologues have been measured for both ortho and para states of H2. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms Daa, Dbb, and Dcc for H2 were required to fit the ortho state of hydrogen, as well as a nuclear-spin rotation constant Caa. The values of the nuclear quadrupole coupling constant of gold are Xaa=-817.9929(35) MHz, Xbb=504.0(27) MHz, and Xcc=314.0(27). This is large compared to the eQq of AuCl, 9.63 312(13) MHz, which indicates a strong, covalent interaction between gold and dihydrogen

Computational Study of the Rovibrational Spectrum of CO₂-CS₂

A new intermolecular potential energy surface, rovibrational transition frequencies, and line strengths are computed for CO2-CS2. the potential is made by fitting energies obtained from explicitly correlated coupled-cluster calculations using an interpolating moving least squares method. the rovibrational Schrödinger equation is solved with a symmetry-adapted Lanczos algorithm and an uncoupled product basis set. All four intermolecular coordinates are included in the calculation. in agreement with previous experiments, the global minimum of the potential energy surface (PES) is cross shaped. the PES also has slipped-parallel minima. Rovibrational wavefunctions are localized in the cross minima and the slipped-parallel minima. Vibrational parent analysis was used to assign vibrational labels to rovibrational states. Tunneling occurs between the two cross minima. Because more than one symmetry operation interconverts the two wells, the symmetry (-oo) of the upper component of the tunneling doublet is different from the symmetry (-ee) of the tunneling coordinate. This unusual situation is due to the multidimensional nature of the double well tunneling. For the cross ground vibrational state, calculated rotational constants differ from their experimental counterparts by less than 0.0001 cm-1. Most rovibrational states were found to be incompatible with the standard effective rotational Hamiltonian often used to fit spectra. This appears to be due to coupling between internal and overall rotation of the dimer. a simple 2D model accounting for internal rotation was used for two cross-shaped fundamentals to obtain good fits

The Carbon Mainframe Structure of cis-trans-1,3-difluoroacetone

The carbon-13 backbone structure of 1,3-difluoroacetone has been obtained and reported for the first time. This was achieved through the collection of singly substituted 13C isotopologue rotational spectra at each carbon position. The rotational constants for each isotopologue have been determined and are reported for the first time. Kraitchman coordinates and second moment analysis verify the structure determined by previous literature studies and are presente

Structure and Barrier to Methyl Group Internal Rotation for (CF₃)₂CFCF₂OCH₃ and Its Isomer n-C₄F₉OCH₃ (HFE-7100)

The hydrofluoroether C 4F 9OCH 3 (methoxynonafluorobutane, HFE-7100) has been studied by chirped pulse Fourier transform microwave spectroscopy as vapor from the liquid participates in a supersonic expansion of argon. Two isomers are present, (CF 3) 2CFCF 2OCH 3 and n-C 4F 9OCH 3, and in each case the rotational spectra of only one, dominating, conformer has been assigned. Rotational constants, centrifugal distortion constants, and barriers to methyl group internal rotation for the observed species have been experimentally determined for the first time. We note that Rays asymmetry parameter for the (CF 3) 2CFCF 2OCH 3 isomer is 0.007 083(1), indicating almost perfect asymmetry. Also, electronic structure calculations show an extremely short C(frame)-O ether bond length of 1.337

¹¹⁷Sn and ¹¹⁹Sn Hyperfine Structure in the Rotational Spectrum of Tin Monosulfide Recorded Using Laser Ablation-source Equipped, Chirped-pulse Fourier Transform Microwave Spectroscopy

Tin metal has been ablated with pulsed radiation from a Nd:YAG laser (λ = 1064 nm). Carbonyl sulfide, diluted in high pressure argon, has been pulsed into the resultant Sn plasma. One of the results of this experiment has been the production of SnS. These events have allowed a rotational spectrum of tin monosulfide to be studied using a chirped-pulse Fourier transform microwave spectrometer. the resolution of the spectrum obtained was sufficient to observe hyperfine structure from the 117Sn and 119Sn-containing SnS molecules. Tin nuclear spin-rotation hyperfine constants are reported for the first time

Chirped-pulse Fourier Transform Microwave Spectroscopy of Perfluoroiodoethane

The pure rotational spectrum of perfluoroiodoethane between 8.0 and 11.9 GHz has been measured on a search accelerated, correct intensity Fourier transform microwave (SACI-FTMW) spectrometer. the spectra is dense with 247 measured transitions in the given region. Only the anti conformer was observed for which rotational constants are reported. Nuclear electric quadrupole coupling constants due to the iodine-127 were determined and are reported. Also, two dipole forbidden/quadrupole allowed Δ J = 2 transitions were observed in the spectra. the observation of these transitions has been rationalized on the basis of near degeneracies between energy levels connected by χab

Conformational Energies of C₄F₉OC₂H₅ (HFE-7200)

A chirp Fourier transform microwave spectrometer has been used to record the rotational spectra of two isomers of the hydrofluoroether C4F9OC2H5 (ethoxynonafluorobutane also known as HFE-7200) between 7.8 and 16.2 GHz. the target compound was spectroscopically examined as it participated in a supersonic expansion of argon. Four separate rotational spectra have been identified amongst the congested data. Spectroscopic parameters are presented for each species. the structures of all four species have been identified by exploring the multi-dimensional potential energy surfaces using quantum chemical calculations

Low-Cost, Balle-Flygare-Type Cavity Fourier Transform Microwave Spectrometer and Pure Rotational Spectroscopy Laboratory for Teaching Physical Chemistry and Astronomy

Few laboratory exercises exist that introduce undergraduate students to both the concepts and instrumentation used in rotational spectroscopy. Because of this gap in undergraduate laboratory training, a teaching laboratory for the pure rotational spectroscopy of benzonitrile has been developed and reported. Owing to benzonitrile\u27s recent discovery in space, the molecular spectroscopic technique and target are applicable to both the physical chemistry and astronomy disciplines. Because of the size of the dipole moment and relative safety of the molecule chosen, the laboratory approach allows undergraduates to directly load, tune, measure, and assign spectra using the same quantum chemical approaches and spectroscopic assigning tools available to a researcher in the field. Concepts taught in this laboratory include the rigid and semirigid rotor, as well as low-level nuclear electric quadrupole coupling Hamiltonians. To minimize the budget and allow the students to get hands-on training with the rotational spectroscopy instrumentation, an interactive, low-cost, Balle-Flygare-type, cavity Fourier transform microwave (FTMW) spectrometer of research-grade quality was developed and is reported. Implementation of the laboratory exercise, time of exercise, and student response to the exercise is also reported

CHIRPED PULSE FOURIER TRANSFORM MICROWAVE SPECTROSCOPY OF SnCl

Author Institution: Department of Chemistry, University of North Texas, 1155 Union Circle \#305070, Denton, Tx 76203-5017, U.S.ATin metal has been laser ablated with the pulsed fundamental output of a Nd:YAG laser. Chlorine gas dissolved in argon was pulsed into the products of this ablation event. One outcome of this has been the formation of SnCl entrained in a supersonic expansion. The expansion occured between the horn antenna of a chirped pulse, Fourier transform microwave spectrometer and accordingly the pure rotational spectra of SnCl, $X^2\Pi_r$, has been recorded for the first time between 8 and 18 GHz. Spectroscopic constants will be presented