Monitoring chirality with X-rays is appealing to gain local information on asymmetric molecular structures. The most straightforward spectroscopic technique, Circular Dichroism, uses the absorption difference between left and right circularly polarized light and has long been used in the optical regime. This difference is small and ongoing efforts are being made to attain the required sensitivity with X-rays. After discussing the unique insights offered by chirality-sensitive X-ray spectroscopies, we will address the challenges associated with implementing X-ray Circular Dichroism. Alternatively, other less commonly used spectroscopies are sensitive to molecular chirality. They rely on nonlinear interactions or on the use of the orbital angular momentum (OAM) of light rather that its polarization. For nonlinear interactions, two theoretical propositions will be discussed relying on second- or third-order interactions. Finally, dichroic measurements with twisted beam carrying an OAM value will be presented.

Over 270 distinct molecules have been detected in the interstellar medium (ISM). Chemical kinetics models are used to elucidate the formation mechanisms of these species under astrophysical conditions, and these models require accurate temperature-dependent rate coefficients for gas-phase reactions. The combination of laser-induced fluorescence (LIF) with uniform supersonic molecular beams (i.e., CRESU) has proven to be a powerful method for measuring total rate constants. In recent years, there has been considerable interest in coupling chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy with the CRESU method, but the high density environment of the uniform flow causes rapid rotational dephasing, dramatically limiting its sensitivity. The extended laval nozzle designed by the Suits group at University of Missouri-Columbia has been successful in measuring a rate coefficient of HCO with O2 using REMPI spectroscopy at 20K (J. Chem. Phys. 159, 214201 (2023)). In addition they successfully coupled the extended laval nozzle to a Chirped-Pulse Fourier-Transform millimeter wave (CP-FTmmW) spectrometer. Here we present the incorporation of an LIF spectrometer with an extended Laval nozzle. A small hole is drilled into the side of the nozzle extension and is sealed with a UV fused silica window to provide optical access. Impact pressure measurements and computational fluid dynamics simulations have been performed to ensure that the introduction of the window does not affect flow uniformity. A telescope assembly is mounted to the exterior of the Laval nozzle extension and is used to couple the fluorescent light into an optical fiber for delivery to a monochromator and detector. This setup allows for measurement of fluorescence within the extended nozzle region and provides an important complement to CP-FTMW measurements which are performed downstream of the extended Laval nozzle following a free expansion. Details of the design and performance of the LIF spectrometer will be discussed.

Cryogenic ion vibrational spectroscopy (CIVS) is a technique which monitors the loss of a cryogenically-condensed “tag” molecule from a gas-phase ionic complex due to IR photodissociation. Reflectron-time-of-flight (Re-TOF) mass spectrometers are typically used for CIVS and only allow for spectroscopic analysis of one m/z complex at a time due to their separation in the TOF region. Replacement of the TOF mass analyzer with a quadrupole ion trap would allow for higher throughput multiplexed spectroscopy experiments where IR spectra of more than one m/z species are obtained in one scan. However, this would also require very selective mass filtration in order to eliminate multiple untagged parent ions before spectroscopic analysis. Here, we present a novel complex square waveform implemented on a home-built digital linear ion trap (LIT) mass spectrometer being developed for multiplexed CIVS. The LIT is driven by variable frequency, fixed amplitude square waves, as opposed to traditional quadrupolar ion trapping with variable amplitude, fixed frequency sine waves. Additionally, a complex square waveform can selectively excite the parametric resonances of ion motion within the quadrupole trap, introducing precise mass filtration capabilities. The driving square waves and complex excitation waveform are both produced by a combination of Direct Digital Synthesis circuitry and high voltage MOSFET-based switches. We demonstrate that this square parametric excitation signal can resonantly excite specific m/z species to eliminate them from the trap before mass analysis. Application of this signal during ion ejection also results in improved mass resolution and instrument performance.

Laser vaporization is a versatile source capable of generating various clusters of interest. Despite the cooling effect of supersonic expansion, anionic clusters produced by laser vaporization often retain a significant amount of internal heat. Hot bands introduced by high internal temperature can greatly conjecture the high-resolution spectra. Our group has recently made advancements by coupling a cryogenically controlled 3D Paul trap with a laser vaporization source. Moreover, since hydrogen is used as part of the buffer gas to arrest and trap ions, the high-speed molecular beam can induce collisional reactions with hydrogen, leading to the formation of hydride clusters. In this poster, I will delve into our recent progress in high-resolution photoelectron imaging of BiB- clusters, in which all the possible electronic transitions can be clearly resolved by the first time for such systems. BiBH- was also generated by the ion trap. High-resolution photoelectron imaging and bond length calculation indicates that a formal Bi-B triple bond is formed by the addition of an extra hydrogen atom. We extended our investigations to BiB2- and BiB3- clusters, uncovering valuable insights into their properties and behavior.

We report on our recent studies on ion-Rydberg atom interactions performed in the ultra-cold quantum regime, using a high-resolution ion microscope. This apparatus provides temporal and spatial resolved images of charged particles with a resolution down to 200nm. The interaction between an ion and a Rydberg atom leads to a rich structure of pair potentials, which can be used to study molecular states as well collisional dynamics. The ion induces a stark splitting in the Rydberg atom, which leads at small distances to a manifold of avoided crossing. If the potential curves feature a local minimum it is possible to photo-associate molecules. With the help of our ion microscope we can take spatially resolved images of the emerging dimer. When kicking one of the atoms it is even possible to observe molecular vibrations in real space. In a second experiment we focused on the collision dynamics of a Rydberg atom and an ion. Due the complexity of the pair states and the large number of avoided crosses we can observe a sequence of diabatic and adiabatic transition during the collision.

Multiple Quantum Coherence (MQC) NMR uses multiple coherent pulses to form quantum coherences (MQCs) between 1H, 13C, 15N, etc. spin states. Spectra are acquired by either changing time delays between multiple pulses to resolve the MQC phase oscillations or changing the frequencies across spin resonances. The spectral range of NMR is very narrow and can be easily spanned by the pulse bandwidth. Townes received a Nobel prize for realizing that an optical analog of NMR could be created using stimulated emission. Much effort has been made to realize a true optical analog of MQC NMR but it has been restricted by the short coherence times of vibrational and electronic states. This talk will demonstrate how the frequency method succeeds in creating an MQC NMR analogue that spans the entire electromagnetic spectrum, creates coherent control of chemical reactions, and correlates coupled cross peaks of vibrational, electronic, and valence band core states.

Metrology-grade spectroscopic measurements of molecules are of high importance for numerous applications such as testing fundamental physicsM. R. Fiechter & al, The Journal of Physical Chemistry Letters 13, 42, (2022)nd astrophysicsC. Puzzarini & al, PCCP 12, (2020) Because it is suspected to exhibit a high sensitivity to a potential proton-to-electron mass ratio variationP. Jansen & al, J. Chem. Phys. 140, (2014) the ν₂=1, rotation-inversion 2_1,s←1_1,a transition of ammonia at 140.142 GHz is of great interest and requires to largely improve the laboratory measurements. In this context, a thorough investigation of this transition has been conducted through Doppler-free double resonance techniqueS. Ghoshal & al, The Journal of chemical Physics 83, (1985)^, A. Foltynowicz al, PRL 126, (2021)uR. Santagata al, Optica 6, (2019))https://www.refimeve.fr/.

Laser Induced Breakdown Spectroscopy (LIBS) was applied for the spectrochemical analysis of cultivated soil to evaluate the impact of irrigating water quality on the soil chemical composition. Here main focus was on detection of essentials nutrients like Al, Mg, Ca, Fe, S, Si, Na, P, K and moderately toxic metals As, Ba, Cr, Cu, Sn, Mn, Ni , Zn in the cultivated soil. A pulsed Nd:YAG laser operating at 1064 nm was employed to record the laser induced plasma emission spectra of the soil irrigated by various water resources. For recording of laser induced emission spectra, certain amount of the fine powder of each soil samples irrigated from various water sources were taken and palletized using hydraulic press. The pellets were then exposed to an high energy laser pulse for generation of plasma plume. The concentration of above-mentioned elements was estimated using calibration free (CF)-LIBS and standard calibration curves (CC)-LIBS methods. To make sure the optimum experimental conditions for the precise assessment of elemental composition of irrigated soil, the local thermodynamic equilibrium and the creation of optically thin plasma conditions were fulfilled by determining the plasma parameters like electron temperature (Te) and electron number density (Ne). In addition, using a standard Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) was applied as a mean of validating the quantitative results of LIBS, it was found that the results from both methods were remarkably consistent. *The support by King Fahd University of Petroleum and Minerals is highly acknowledged.

The advancement of carbon nanomaterials has made this extensively exploited chemical element ubiquitous in nanoscience exploration. Carbon dots are novel carbon nanomaterials capable of wavelength-tunable emission with nanoscale photophysical performance without a size dependence. Fluorescence intermittency or blinking in carbon dots is attributed to energy transfer between defects on the surface. Current theories of carbon dot emission involve a mechanism for these blinking events based on competing nonradiative pathways. However, there has been no determination if the number of emitters on a single carbon dot exceeds one, nor how multiple emitters might contribute to blinking. Through simultaneous single-molecule spectroscopy and emission polarization measurements, we identified multiple emitters from single carbon dots based on changes in emission polarization after individual carbon dot blinking events. The simultaneous spectral acquisition provides spectroscopic signatures that show that the emitters are chemically similar in each blinking events. Through this unique multidimensional single-molecule technique, we conclude that that there is support for several but not many emitters contribution to the emission of carbon dots.

Absolute, time-resolved population of a metastable electronic state of molecular nitrogen, N₂(A³Σ_u⁺,v=0), is measured in a heated plasma flow reactor excited by a ns pulse discharge burst, by Tunable Diode Laser Absorption Spectroscopy (TDLAS) using a Distributed Feedback (DFB) laser. A slow flow (1 slm) of N₂ or 1000 ppm NO-N₂ gas mixture in the reactor is heated by a tube furnace maintained at T=800-1000 K, at pressures of P=50-300 Torr. A diffuse plasma in the flow channel made of quartz is generated using a repetitively pulsed, double dielectric barrier, ns discharge in a plane-to-plane geometry. The discharge is operated in burst mode, at the pulse peak voltage of ≈ 30 kV, pulse duration of ≈ 10 ns, pulse repetition rate of 100 kHz, and burst repetition rate of 10 Hz, up to 20 pulses per burst. The discharge gap is 1 cm and the length of the plasma (i.e. absorption path) is approximately 8 cm. N₂(A³Σ_u⁺) molecules in the plasma are generated by electron impact excitation of N₂(B³Π_g) and N₂(C³Π_u) states, followed by their cascade quenching. The laser is tuned across the absorption line, N₂(B³Π_g,v^′=0,j^′= 32 ← A³Σ_u⁺, v^"=0,j^" = 32) centered at 1028.427 nm, at 100 kHz - 1 MHz, and the absorption signal is measured by a high bandwidth detector. The laser output wavelength is monitored using an etalon and another high bandwidth detector. At all operating conditions, the absorption signal is fully resolved in time, which was verified by comparing the data taken 100 kHz and 1 MHz with the signal taken when the laser was parked at the absorption line center. The sampling rate of the present measurements is 200 kHz - 2 MHz, i.e. the data points are taken every 500 ns - 5 μs, with the temporal uncertainty of 50 ns - 500 ns, respectively. The data are used to infer the line pressure broadening coefficient and its temperature dependence. Since N₂(A³Σ_u⁺) is a precursor to excited metastable N and O atoms, the results will be used to study their associative ionization, N^∗ + O^∗ → NO⁺ + e⁻ , one of the dominant ionization processes in hypersonic flows. This study demonstrates the feasibility of this approach for time-resolved N₂(A³Σ_u⁺) measurements in pulsed flow facilities, behind strong shock waves and in hypervelocity expansion flows.