In the present scenario, a number of approaches are available for the elemental analysis of drug samples but quick and cost-effective techniques are vital in the drug manufacturing industry. During the last few decades, Laser Produced Plasma which is also known as Laser Induced Breakdown Spectroscopy (LIBS) has been adopted as a viable spectroscopic analytical technique in the various field. In the pharmaceutical arena, a wide range of applications including the analysis of the active pharmaceutical ingredients (API) and excipients etc., the utility of LIBS have begun to emerge. The steroids of different brand and dosages have been taken for the analysis. LIBS is basically atomic spectroscopic technique however, in the present approach, molecular signatures of the drug sample were also investigated using LIBS and being conformed to the complementary techniques i.e. Raman and FTIR spectroscopy.

Laser Induced Breakdown Spectroscopy (LIBS) spectra of some WHO listed essential pharmaceutical drugs have been recorded in air and argon atmosphere. The spectral signatures of characteristic molecular emission of the CN violet band system and C2 Swan band system along with the atomic and ionic lines of various elements are observed in the LIBS spectra of the drug samples. We have measured the intensity of these molecular bands. With the help of the intensities of these bands, an attempt has been made to correlate the CN violet and C2 swan band with the chemical structure of the molecule present in the drugs. The essential drugs of different brands have been taken for the LIBS analysis. PCA (a multivariate method) has also been applied on the LIBS dataset for the discrimination purpose of the drugs which have a similar composition. In addition to this, for the confirmation of the molecules present in the drug, complementary molecular spectroscopic techniques, called Raman and FT-IR spectroscopy, have been applied to find out the molecular spectra of these drug samples. With the implementation of the above approach, it is established that LIBS techniques may be used as an online drugs analysis technique in pharmaceutical industries.

Broadband laser absorption spectrometers have enabled sensing of temperature, pressure and absorber mole fraction in gaseous systems with high sensitivity and precision. However, recovering thermodynamic conditions from the measured spectrum can be complicated by the need to correct for the background intensity spectrum of the laser source (the ‘baseline’). Baseline correction becomes challenging for highly modulated laser spectra (e.g. from non-linear spectral broadening processes or etalon effects in the optical system) as well as in the presence of broadband absorption from large molecules (e.g. hydrocarbons). In this talk, we demonstrate a technique for measuring temperature, pressure, and species concentration from an absorption spectrum without the need to correct for the laser intensity spectrum. This technique is based on the time domain description of absorption spectroscopy – where the typical absorption features manifest as the temporal dynamics of the excited molecules. We demonstrate the fitting technique by accurately measuring temperature and pressure from the broadband spectrum of water vapor over a range exceeding 1000 K. Further, we apply the technique to a broadly absorbing mixture by accurately recovering species concentrations from a mixture of ethane and methane. This mixture absorbs continuously for more than 500 cm⁻¹ in the near-infrared, and thus poses a significant challenge for traditional baseline correction methods. By eliminating the need to correct for the laser intensity spectrum, our results address a significant limitation of broadband laser absorption spectroscopy for sensing applications.

High resolution coherent multidimensional spectroscopy is a powerful new tool that can be used to overcome difficulties encountered with other forms of spectroscopy. The 2D spectra have reduced congestion and show easily recognizable patterns, even for molecules that yield patternless 1D spectra Furthermore, the peaks are automatically sorted by quantum number and species. The 3D technique further reduces congestion, provides selectivity, and can be used to generate unique 3D rotational patterns. This talk provides an overview of newly developed high resolution coherent 2D and 3D techniques.

r0pt Figure Femtosecond coherent anti-Stokes Raman scattering (fs-CARS) is a non-linear spectroscopic technique that has been widely used in various combustion related environments to measure the temperature and species concentration information. On the other hand, self-phase modulation (SPM) describes a Kerr-like effect in which an ultrashort pulse accumulates nonlinear phase as it propagates through the gas medium like N₂. As a result, the application of fs-CARS in the high pressure environment will inevitably need to deal with SPM influence especially when at high laser intensities. We evaluated the SPM effects by measuring the optical spectra of the ultrashort pulses as well as the fs-CARS spectrum transmitted through our custom-designed high-pressure vessel. Different SPM patterns and the extent of SPM were evaluated for gaseous species like N₂, CO₂ and CH₄. With the suppression of SPM by reducing the laser intensity, fs-CARS spectrum in pure N₂ was successfully fitted for pressure range from 1 to 10 bar. This study is meaningful not only for the study of fs-CARS measurement but also for all the other ultrafast spectroscopic studies at high pressure conditions, especially when the laser beams need to be focused or if the optical path inside the high pressure chamber is significant.

Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS), taking advantage of combining the cavity enhancement and frequency modulation techniques, provides an excellent method to enable ultra sensitive detection. The advantage of noise immunity enables for shot-noise limit detection, particularly for those molecules with ultra-small dipole moments, such as overtone transitions and symmetrical molecules, NICE-OHMS provides a superior strategy to achieve sub-Doppler saturation spectroscopy. Using an optical cavity with a high finesse > 100,000, in our previous work, we reported the sub-Doppler saturation NICE-OHMS spectroscopy for nitrous oxide (N₂O) overtone transitions using the quantum-dot (QD) laser developed at 1.28 μm. At a pressure of several mTorr, the saturation dip is observed with a full width at half-maximum of about 2 MHz. The noise equivalent bandwidth-reduced sensitivity is 1.6×10⁻¹¹cm⁻¹Hz^−1/2. The QD laser is then locked to this dispersion signal with a stability of 15 kHz at 1 s integration time. We demonstrate the potential of the (N₂O) as a marker because of its particularly rich spectrum in the vicinity of 1.28 μm, where there are several important forbidden transitions of atomic parity violation measurements. In current work, we have used a new QD laser system coupled to a high finesse cavity for NICE-OHMS of the H₂ overtone transition S1, where the dipole moment is only 30 mD. The QD laser developed at 1.16 μm is gain-chip based and mounted in an integrated mechanism system to reduce the passive laser linewidth. The cavity finesse was measured to be 234,000 (8000) by using laser-swept cavity ring-down time measurements. After the laser locking, the laser power will be amplified by a fiber amplifier to satisfy saturation condition to achieve sub-Doppler NICE-OHMS spectroscopy.

l0pt Figure The five lowest-lying electronic states of nickel hydride (NiH) are usually labeled ²∆_5/2, ²Π_3/2, ²∆_3/2, ²Σ⁺_1/2 and ²Π_1/2, although there is significant mixing between them. These states arise from the d⁹ electron configuration of Ni⁺, perturbed by an H⁻ ligand. A variety of vibrational levels has been observed in each, and the aggregate data set has been well modelled as a `supermultiplet' by the Field groupJ. A. Gray, M. Li, T. Nelis and R. W. Field, J. Chem. Phys. 95, 7164 (1991) For the deuterated isotopologue NiD, only the ²∆_5/2, ²Π_3/2 and ²∆_3/2 states have been reported in the literature. A multi-isotope supermutiplet fitting including both the NiH and (more limited) NiD dataM. Abbasi, A. Shayesteh, P. Crozet and A. J. Ross, J. Mol. Spectrosc. 349, 49 (2018)rovided predictions for the two Ω = 1/2 states of the NiD supermultiplet. Experimental observation was needed to validate (and improve) the model. We report on laser-induced fluorescence experiments conducted both at the University of New Brunswick and at Université Lyon 1 in which the ²Σ⁺_1/2, v=0,1,2 and ²Π_1/2,v=0,1 levels of NiD were identified and rotationally analyzed. The existing multi-isotope supermultiplet model proved remarkably accurate in predicting the energy and structure of these Ω = 1/2 states. In addition, a higher-lying Ω = 1/2 electronic state [16.7]0.5 has been identified in NiD, with no obvious analogue in NiH. The [16.7]0.5-²Σ⁺_1/2 and [16.7]0.5-²Π_1/2 transitions proved to be a rich source of information about the two lower states.

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Footnotes:

J. A. Gray, M. Li, T. Nelis and R. W. Field, J. Chem. Phys. 95, 7164 (1991). M. Abbasi, A. Shayesteh, P. Crozet and A. J. Ross, J. Mol. Spectrosc. 349, 49 (2018)p

Matrix-assisted laser desorption ionization (MALDI) is a widely used mass spectrometric technique for the mass analysis of biomolecular compounds. For over three decades since its development a considerable effort has been devoted to increasing the mass resolution and efficiency of MALDI. However, due to a lack of a detailed description of the fundamental processes, underlying the initial ionization, leaves optimization of the method at a trial-and-error endeavor. Generally, MALDI exploits a laser pulse to commence an ionization event where ions, neutrals, and electrons are ejected from the substrate surface into the gas phase (plume). Here we used 3D momentum imaging of laser desorption ionization to investigate the ionization dynamics of dihydroxybenzoic acid (DHB) with different laser pulse durations. Varying the pulse duration between femtoseconds and picoseconds present significantly different dynamics that are reflective of the velocity distributions. These findings suggest that MALDI is not a single molecule process, rather a collective intermolecular phenomenon.

Surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) provides a pathway to efficiently absorb and confine light to nanoscale surface electrons, thereby bridging photonics and photoelectrochemistry. This not only produces the giant Raman intensity enhancement in surface-enhanced Raman spectroscopy (SERS), but also results in plasmon-driven chemical reaction on metal nanostructures. We have studied the surface-enhanced Raman spectra of p-aminothiophenol adsorbed on silver electrodes of nanostructures. In this work, we studied SPR-enhanced photoelectrochemical synergistic reactions by SERS to improve chemical reaction activity and examine changes in reaction selectivity. We first demonstrate that hot carriers arising from SPR decay contribute to the surface catalytic coupling reaction of PATP on a silver NP electrode. Then, by using potential step electrochemical SERS, we further inspect the kinetics of the surface catalytic coupling reaction by monitoring the time-dependent SERS intensity of the characteristic band at 1436 cm⁻¹, which can be attributed to the stretching vibration of the N=N double bond of p,p’-dimercaptoazobenzene (DMAB). When synergistically combined with the modulation of pH at electrochemical interfaces, SPR-enhanced photoelectrochemical reactions can be further gain reaction efficiency and selectivity for the formation of DMAB and other surface species at higher potentials. The electrochemical SPR effect provides a viable approach for studying the photoelectrochemistry through combining SERS at the interface of nanoparticle-modified metal electrodes and electrolytes.