Abstract: We have begun introducing complex-valued principal component regression (PCR) into spectroscopy. Unlike traditional methods that are constrained to either the real or imaginary axis, this approach allows principal components (PCs) to span the entire complex plane. While this added flexibility enhances modeling capabilities, it also introduces challenges, as existing tools often fail to identify optimal solutions. To address this, we explored two different strategies for computing eigenvectors. The most natural approach is to apply singular value decomposition (SVD) directly to the matrix of complex refractive index spectra. As an alternative, we combined the eigenvectors of the imaginary parts determined by SVD with their Kramers–Kronig transforms, which resulted in 2N possible superpositions for N PCs. Although the optimal solution may still be unknown, the proposed second method for complex-valued PCR consistently outperformed conventional PCR in the systems investigated. This highlights its potential to enhance data analysis in infrared and Raman spectroscopy.

New from Applied Spectroscopy!
Complex-Valued Chemometrics in Spectroscopy: Principal Component Regression
Read more: https://doi.org/10.1177/00037028251393273
#SAS #Spectroscopy #Complex #Chemometrics #PCA #Regression

New from @applspecpractica.bsky.social!

Detection of #Lead (II) Chromate inn #Cinnamon

Read the full 🔓open-access🔓 abstract here: https://loom.ly/McTfJb0

#SAS #spectroscopy #publichealth #foodsafety

Have you signed up to get issues of Applied Spectroscopy Practica to your inbox? If not what are you waiting for! Don't miss an issue, sign up today: https://bit.ly/3Q9xq1N #SAS #AppliedSpectroscopyPractica

We hope everyone is enjoying the Spring SciX at the University of Exeter, UK. If you are attending, please be sure to share your experience and tag SAS! #SAS #SpringSciX

Abstract: In the first paper in this series, we proposed the use of a set of colored LEGO blocks as “standard” samples for the evaluation of fluorescence avoidance and mitigation schemes in Raman spectroscopy, as well as for use to evaluate the instruments’ performance on dark samples. In the second paper we described the spectra obtained on the same blocks from ten different handheld Raman instruments. We found that the combination of a series of colored blocks (white, yellow, red, and blue), and successively darker tone blocks (white, gray, and black) do challenge these instruments and shed light on the ways that their manufacturers have optimized these instruments in specific areas and for different purposes. In this paper we extend the work using an advanced Raman data collection technique: A fast-repetition-rate, short-pulse, laser with a single-photon avalanche photodiode (SPAD) array detector capable of providing a time-sequence output, commonly known as a “time-gating” or “time-resolved” approach. The results are evaluated and compared to those in the first two papers. In addition, X-ray fluorescence (XRF) spectra were also collected to confirm identifications of some of the blocks’ inorganic pigments, which were detected via their Raman spectra.

New from Applied Spectroscopy!
Evaluation of the Raman Spectra of LEGO Blocks and Fluorescence Avoidance Using Pulsed Laser Excitation and Time-Resolved Detection
Read more: https://doi.org/10.1177/00037028251400397
#SAS #Spectroscopy #Raman #Fluorescence #Avoidance #TimeResolved

New from @applspecpractica.bsky.social!

Molybdenum–Gold Nanoclusters Using 2-Mercapto-5-nitrobenzimidazole as Ligand for Sensing Guanosine and Mg2+ Ions Through a Fluorescence Turn Off–On Mechanism

Click here: https://loom.ly/ZxzuRWo

CALL FOR ABSTRACTS: The deadline to submit an oral paper for the Eastern Analytical Symposium is May 1st! For more submission details and to submit an abstract, visit: https://loom.ly/XyvF6f0

Thank you to everyone who presented and attended the Fourth Virutal Student/Early Career SLAM 2026.

Thank you to the Coblentz Society for sponsoring this event with us. We look forward to doing it again next year.

#SAS #Spectroscopy #SLAM2026 #StudentsInScience #EarlyCareer #SciX

Abstract: A technique for quenching-independent, two-photon absorption laser-induced fluorescence (TALIF) measurements of atomic nitrogen in high-enthalpy facilities is presented. The technique relies on high-laser intensity, which results in the photoionization rate dominating other depopulation channels for the induced excited state. The photoionization-dominated technique is applied here to study the distribution of atomic nitrogen in the vicinity of an ablating graphite sample in a plasma plume. Three different plasma conditions are investigated: a 17 MJ/kg air plasma delivering 145 W/cm2 to the graphite surface, an 18 MJ/kg air plasma delivering 195 W/cm2, and a 24 MJ/kg nitrogen plasma delivering 85 W/cm2. The number density of atomic nitrogen is measured along the stagnation streamline of the flow on the graphite sample in each case. The highest number densities are observed in the nitrogen plume, as would be expected given the pure nitrogen composition and high enthalpy. The 195 W/cm2 air condition has the second-highest atomic nitrogen distribution, followed by the 145 W/cm2 air condition. This technique may provide a valuable method for studying atomic nitrogen, an important species to air/carbon gas–surface interaction at hypersonic-relevant conditions, in high-enthalpy facilities.

New from Applied Spectroscopy!
Quenching-Independent Two-Photon Absorption Laser-Induced Fluorescence of Atomic Nitrogen in High-Enthalpy Air–Carbon Gas–Surface Interaction
Read more: https://doi.org/10.1177/00037028251409832
#SAS #Spectroscopy #TwoPhoton #TALIF #nitrogen #fluorescence

👉 Read more: bit.ly/4slSe3I

#SAS #Spectroscopy #Awards #Emeritus #Honorary #ScientificExcellence

2026 SAS Honorary Membership Award Recipients
🏆Mike Carrabba, Ph.D. (Droplet Envea Group)
🏆Heidi Goenaga Infante (LGC)
🏆Jürgen Popp (Leibniz Institute of Photonic Technology)

2026 SAS Emeritus Membership Award Recipients
🏆John M. Chalmers, CChem FRSC
🏆Geoffrey N. Coleman

We are proud to recognize this year’s Emeritus and Honorary members, honoring their outstanding contributions, leadership, and lasting impact on the field of spectroscopy and the Society.

👏 Congratulations to these distinguished individuals on this well-deserved recognition!

Abstract: Optical identification of liquid droplets, aerosols, or thin films is critical for many applications. While reference spectra are sometimes available for such measurements, they are not always applicable to the observed spectrum or the given sample morphology. Reference spectra for many forms can be modeled, however, if the n/k vectors (real and imaginary refractive indices) are available. In previous work we have reported protocols to determine the n/k vectors for dozens of liquids, primarily in the mid-infrared (MIR) spectral range from 7500 to 400 cm–1. In this work we extend the spectral range into the near-infrared (NIR) region, demonstrating a method to measure and merge the data sets to create composite n/k data ranging from 10 000 to 400 cm–1 (1.0 to 25 µm) with absorbance fidelity spanning over four orders of magnitude, and vastly improved signal-to-noise in the NIR. The precision of the composite data is evaluated for three different liquids, focusing primarily on the steps for converting the raw absorbance spectra to k values. The variability in both MIR and NIR data as well as in the final n/k vectors is also investigated for several liquids. For typical liquids, the overall variability (reported as 2σ) in the final n and k-vectors is determined to be ∼0.4% and 3%, respectively. Finally, the derived n/k data are used to calculate absorbance spectra for aerosol droplets, showing marginal variability due to the typical measurement errors in the final n/k vectors.

New from Applied Spectroscopy!
Extension of Complex Refractive Index Measurements to the Near-Infrared for Liquids: Methodology and Uncertainty Analysis
Read more: https://doi.org/10.1177/00037028251399225
#SAS #Spectroscopy #complex #Refractive #Index #NIR

the Society for Applied Spectroscopy (SAS). #SAS #Spectroscopy #SLAM2026 #StudentsInScience #EarlyCareer #SciX

Good luck to all of the students and early-career researchers with the Fourth Virtual Student/Early Career SLAM. We look forward to hearing about all of your work!

Register to attend: bit.ly/4sLIzED

View the presenters here: bit.ly/4sn4sJt

Sponsored by the Coblentz Society and

Applied_Spectroscopy_Practica_04_01 Experience our interactive, profoundly engaging digital publication!

The latest issue of Applied Spectroscopy PRACTICA is here! @applspecpractica.bsky.social

Click here to read the full, 🔓open-access🔓 issue: https://loom.ly/lK6Y70k

#SAS #spectroscopy #appliedscience #openaccess

#SAS #Spectroscopy #Sponsorship #Advertising #Marketing

🚀 Looking to grow your visibility in the spectroscopy industry? The SAS Advertising Prospectus offers sponsorship and advertising opportunities to showcase your brand and connect with a global, engaged audience.

👉 View the prospectus: bit.ly/4q5vT9u

REMINDER: ❗Tomorrow❗at 12 pm EST is the 2026 Virtual Early Career and Student Slam!

Register to attend: https://bit.ly/4sLIzED

View the presenters here: https://bit.ly/4sn4sJt

#SAS #Spectroscopy #SLAM2026 #StudentsInScience #EarlyCareer #SciX

Abstract: This paper provides the first temporally resolved visualization of the formation and decay profiles of Thermally induced reflection of sound (THORS) barriers in ambient air, revealing the spatiotemporal characteristics of these novel acoustic barriers. In this work, a 532  nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser coupled with an intensified charge-coupled device (ICCD) is used to Raman image N2 in ambient air, thereby allowing for the visualization of the spatial dynamics of the air density variations at these THORS barriers. Studies were conducted at various ambient temperatures and with air turbulence across the beam path revealing no change in barrier size or shape under typical environmental disturbance conditions. Raman images of a barrier formed by a repetitively pulsed CO laser reveal an abrupt barrier density change between the optically depleted region and the surrounding air, with the slope of the imaged barrier density increasing rapidly during the first 20  ms of barrier formation, indicative of the predicted increase in barrier abruptness associated with enhanced THORS efficiency. As seen in previous temporal studies of THORS barrier efficiencies, these images reveal that multiple laser pulses at an optimized optical frequency are capable of achieving maximum continuous suppression efficiencies through molecular depletion in the optically excited region. These imaging studies revealed that the maximum barrier efficiency required a minimum of eight laser pulses to achieve the desired barrier density change and depletion, agreeing with previous temporal studies that showed in maximum suppression efficiency after 16  ms with one ms excitation laser pulses. Furthermore, visualization of the barrier size revealed that thermal redistribution of the photothermally excited molecules resulted in a THORS barrier approximately 50% larger than the excitation beam width and that this barrier remains constant for as long as 15  ms after the final laser pulse and at laser powers between 50 and 250 W.

New from Applied Spectroscopy!
Spatiotemporal Visualization of the Formation and Decay of Thermally Induced Optical Reflection of Sound (THORS) Barriers in Ambient Air
Read more: https://doi.org/10.1177/00037028251413279
#SAS #Spectroscopy #Raman #THORS #N2

Don't forget, the Spring SciX will be taking place April 14 - 16 at the University of Exeter, UK. For more information, please visit: https://bit.ly/3PDD8sK #SAS #SpringSciX

Abstract: The increasing concern about the presence of pesticides in vegetable leaves has underscored an urgent need for real-time, nondestructive, and accurate detection methods. Traditional methods are reliable but laboratory-based, costly, and unsuitable for field monitoring. In this study, we propose an efficient learning model pipeline that uses hyperspectral reflectance signatures to detect pesticide residue in plant leaves. We extract a comprehensive set of 39 domain-specific features based on vegetation indices, red-edge metrics, spectral statistics, and derivative profiles. To enhance the performance, use a multilayer perceptron to extract more features. A feature fusion module is used to combine both domain-specific features and features extracted by a multilayer perceptron. Further refinement is achieved through a feed-forward attention scoring module that dynamically weights important features. The efficiency of the system is evaluated using an enhanced extra trees classifier, which shows superior classification performance and stability across different feature formats. With cross-validation, our model achieves an accuracy of 94.69%, significantly outperforming conventional classifiers such as convolutional neural networks, support vector machines, and ensemble models such as random forest and extra trees. This framework not only improves interpretability and performance but also provides a foundation for a real-time, on-site pesticide monitoring solution.

New from Applied Spectroscopy!
Advanced #Hyperspectral Signature Processing for Chemical Stress Detection in Vegetable Leaves Using Hierarchical Feature Extraction and Enhanced Ensemble Model
More: https://doi.org/10.1177/00037028251411953
#SAS #Spectroscopy #pesticides #classification #monitoring

🤝 Member Benefit Spotlight:

Another big perk you get when joining SAS is the ability to develop your career through different training and networking opportunities. Learn more about why you should join today: bit.ly/3LRexPF

#SAS #Spectroscopy #MemberBenefits #Networking #ProfessionalGrowth

Your leadership, innovation, and dedication continue to advance the field of spectroscopy worldwide.

#SAS #Spectroscopy #Fellows #Awards #ScientificExcellence

🏆Carol Korzeniewski (Texas Tech University)
🏆C. Derrick Quarles Jr. (Elemental Scientific, Inc.)
🏆Suresh Kumar Kailasa (Sardar Vallabhbhai National Institute of Technology Surat)
🏆Siva Umapathy (Indian Institute of Science)

We are proud to recognize the 2026 SAS Fellows, honoring individuals for their outstanding achievements and contributions to spectroscopy, the profession, and the Society.

👏 Congratulations to this year’s Fellows:

🏆Benjamin T. Manard (Oak Ridge National Laboratory)

Abstract: There is a need for in-field actinide measurements in support of nuclear forensic, safeguards, and environmental monitoring missions. Traditional methods of inorganic/elemental analysis, such as inductively coupled plasma mass spectrometry (ICP-MS), have high operational overheads, making these platforms ill-suited for this task. The liquid sampling–atmospheric pressure glow discharge (LS-APGD) ionization source is a proven microplasma ionization source with significantly reduced operational overhead as compared to ICP-MS; however, most studies to date have focused on coupling the LS-APGD to an ultrahigh resolution Orbitrap mass spectrometer. While the Orbitrap mass spectrometer is a benchtop instrument, it is quite complex with a large footprint and requires extremely low mass analyzer pressures. The Advion ExpressionL compact mass spectrometer (CMS) is a compact, easily transported single quadrupole mass spectrometer platform that was previously coupled with the LS-APGD to measure multielement/metal solutions, albeit not actinides. To this end, this manuscript reports the optimization of the LS-APGD with the Advion ExpressionL CMS mass spectrometer platform specifically for in-field actinide (uranium and thorium) measurements. This is the first report on the optimization of the dual-electrode LS-APGD on the CMS, including a modified ion sampling geometry. This also includes the first analysis of thorium using the LS-APGD, regardless of mass spectrometer coupling. After establishing that the LS-APGD and the mass spectrometer operations could be optimized independently, the LS-APGD discharge conditions were optimized with a design of experiments approach, with the mass spectrometer parameters optimized by a full factorial study. Once fully optimized, limits of detection of 0.2 ng total analyte mass were found for both uranium and thorium, below the EPA requirements for drinking water.

New from Applied Spectroscopy!
Development of a Field-Deployable #Mass #Spectrometry System for Nuclear Forensics Applications Using Liquid Sampling–Atmospheric Pressure Glow Discharge as an Ion Source
https://doi.org/10.1177/00037028251405294
#SAS #Spectroscopy #thorium #uranium #detection

Sponsored by the Coblentz Society and the Society for Applied Spectroscopy (SAS).

#SAS #Spectroscopy #SLAM2026 #StudentsInScience #EarlyCareer #SciX

This event will challenge students and early-career researchers to present their work in a concise, 3-minute format as a way to help them refine their messaging while showcasing their research and networking.

Register to attend: bit.ly/4sLIzED

We hope to see everyone at the Fourth Virtual Student/Early Career SLAM 2026 on April 9 at 12 PM (ET).