Ankit Raj

Includes a large dataset on dipole polarizabilities for 12 diatomics, with their anharmonic and harmonic rovibrational wavefunctions.

Testing the limitations of harmonic approximation in the determination of Raman intensities Raman intensities in molecular spectra are usually computed within double harmonic approximation. This procedure relies on treating a vibrating molecule as a collection of harmonic oscillators and ...

🧪How accurate is the harmonic approximation in Raman intensity calculations? Tested on 12 diatomics using exact anharmonic wavefunctions and distance-dependent polarizabilities. Errors go as high as 10% with F₂ showing the largest deviation.
#RamanSpectroscopy #ComputationalChemistry #Polarizability

The Hektoria Glacier on the Antarctic Peninsula retreated by at least 8 km in two months, a rate nearly 10 times faster than previously measured for a grounded glacier, according to a study in Nature Geoscience. go.nature.com/4nETBYJ ⚒️ 🧪

Cool idea !

Posthandling Spectral Information Enhancement for Single Cell Raman Molecular Mapping Analysis Biochemical analysis of living systems such as single cells benefits greatly from the label-free and low-invasive molecular mapping with Raman microspectroscopy. Sets of Raman spectra at different spatial points are analyzed to generate Raman molecular maps corresponding to specific chemical species. However, human error and subjective data analysis can be technical issues that limit interpretation and its validity. Here, we present an objective data analysis scheme for postprocessing large data sets of Raman spectra for molecular mapping of living cells. The process comprises three steps: (i) Denoising the spectral data set using low-rank approximation; (ii) obtaining an objective background from data points outside the target cell; (iii) subtracting the thus obtained background using Hypothetical Addition Multivariate Analysis with Numerical Differentiation (HAMAND) via an automatically determined coefficient. Through the present analysis, minor Raman peaks, as indiscernible as they are, can be identified and precisely mapped. We demonstrate a quantitative discussion of cellular components after extracting contributions only from a single target cell from a Raman mapping image where multiple cells or parts of other cells are present. This work opens an improved analysis workflow for accurate spectroscopic analysis of living cells with the advantage of identifying minor Raman peaks unambiguously.

By refining how we process Raman information, the study transforms every cell from a blur of chemistry into a clearly textured molecular landscape.

pubs.acs.org/doi/10.1021/...

Testing the limitations of harmonic approximation in the determination of Raman intensities Raman intensities in molecular spectra are usually computed within double harmonic approximation. This procedure relies on treating a vibrating molecule as a collection of harmonic oscillators and ...

When the ‘harmonic’ in Raman modeling hits a sour note.

This study reveals that the widely used double harmonic approximation can misestimate Raman intensities by up to ~10%, even in diatomics due to neglected anharmonic effects. Your Raman intensities might be lying! doi.org/10.1080/0026...

A sequence-activated AND logic probe enables selective detection of senescent cells via dual-input fluorescence signaling. The probe undergoes a two-step reaction: MFB-βgal reacts with β-gal to form weakly emissive MFB-OH, which is then activated by OH⁻ to yield strongly fluorescent MFB-O⁻ (emission at 645 nm). The system functions as an AND gate, requiring both β-gal and OH⁻ inputs to trigger a red-shifted and enhanced fluorescence signal, allowing precise imaging of senescent cells. Would you like a shorter version for journal submission or social media?

🧬 New in Chemical Science:

A dual-logic NIR probe (MFB-βgal) enables precise in vivo imaging of senescent cells by combining β-gal activity with lysosomal alkalinization.

📸 Real-time, false-positive-free detection.

🔗Read for free, here: doi.org/10.1039/D5SC...

Evening light !

GitHub - ankit7540/IntensityCalbr: Intensity calibration procedure for spectrometers using multichannel detectors using spectroscopic intensity ratios as standards. (This is for relative intensity cal... Intensity calibration procedure for spectrometers using multichannel detectors using spectroscopic intensity ratios as standards. (This is for relative intensity calibration and data from all avai...

Colleagues have shown accurate calibration of Raman spectrometer using this dataset combined with analysis of expt data. github.com/ankit7540/In...

GitHub - ankit7540/H2-PolarizabilityMatrixElements: Set of data on polarizability and a python program for the interpolation (of wavelength dependent polarizability) and computation of the matrix elem... Set of data on polarizability and a python program for the interpolation (of wavelength dependent polarizability) and computation of the matrix elements(for rovibrational states) for molecular hydr...

Trying to estimate temperature in nuclear reactor via spectroscopy of H2? Or studying refractive index of H2? Check out this program to obtain polarizability matrix elements of hydrogen molecule from UV to IR wavelengths.
github.com/ankit7540/H2.... For other uses of this dataset see comments.

Toward standardization of Raman spectroscopy: Accurate wavenumber and intensity calibration using rotational Raman spectra of H2, HD, D2, and vibration–rotation spectrum of O2 Wavenumber and intensity calibration of a Raman spectrometer is performed utilizing pure rotational Raman bands ((Δν = 0, ΔJ = ± 2)) of H2, HD, D2 and vibration-rotation Raman bands ((Δν = 1, ΔJ = ± ...

Proper intensity calibration is a rarely discussed aspect in Raman spectroscopy. Wonder why? Its complicated ! Depends on various factors. Checkout these works on intensity calibration using Raman bands themselves and to unprecedented accuracy! doi.org/10.1002/jrs.... and doi.org/10.1002/jrs....

GitHub - ankit7540/Raman-Intensity-Approxmn-Test: Python module implementing the collocation method for 1D ro-vibrational Schroedinger equation. This repo also includes datasets on ro-vibrational wave... Python module implementing the collocation method for 1D ro-vibrational Schroedinger equation. This repo also includes datasets on ro-vibrational wavefunctions and polarizabilities of 12 diatomic m...

Try out your own analysis for molecule of your interest. (Model PES, get wavefunctions and compute matrix elements). github.com/ankit7540/Ra...

Ridgeline chart showing the distribution of global daily air temperature differences from the pre-industrial reference period (1850-1900), for every year between 1940 and 2024. Each individual year resembles a hill, shaded in a darker shade of red and further to the right for warmer years. The trend is clearly towards warmer years, with 2024 standing out as first year above 1.5C.

NEW: 2024 has just been confirmed as the warmest year on record, and the first to breach the 1.5C threshold.

We used a ridgeline (Joy Division inspired) chart to visualise daily temperature anomalies since 1940.

2024 clearly stands out with 100% of its days above 1.3C and 75% above 1.5C.

Raman spectra and structure of hydrogen‐bonded water oligomers in tetrahydrofuran–H2O binary solutions Raman spectra of hydrogen-bonded water oligomers are resolved from concentration-dependent Raman spectra of tetrahydrofuran(THF)–water binary solutions with the use of multivariate curve resolution w....

Wondering how a single water molecule interacts in an ocean of solvent molecules. Check out this work on hydrogen bonding of water with THF at ultra low concentrations, to observe individual molecular complexes in condensed phase! Using Raman Spectroscopy. doi.org/10.1002/jrs....

Polarizability tensor invariants of H2, HD, and D2 We report an exhaustive compilation of wavelength-dependent matrix elements over the mean polarizability (α¯) and polarizability anisotropy (γ) operators for th

Hydrogen is everywhere ! Most abundant molecule in the universe.
If you are studying it using experimental techniques such as Raman spectroscopy, check out this work on polarizability tensor of hydrogen and its rovibrational matrix elements. doi.org/10.1063/1.50...

Happy new year to all :-)

Winter colors ! Merry Christmas to all 😃

Testing the limitations of harmonic approximation in the determination of Raman intensities Raman intensities in molecular spectra are usually computed within double harmonic approximation. This procedure relies on treating a vibrating molecule as a collection of harmonic oscillators and ...

Why Raman intensities cannot be easily predicted with sub 10% error within standard QM softwares and response theory ? Why do observations and DFT results mismatch ?

A critical analysis shows 5 to 10% error even for diatomics due to harmonic approximation ! Check : doi.org/10.1080/0026...

Evaluating stability of a Raman spectrometer for long‐time experiments Temporal stability of the band positions and Raman intensities in series of spectra acquired over tens of hours was studied. The Raman spectrometer operated in a typical air-conditioned laboratory. S...

Microelectronics and associated sensors can be effectively combined to monitor the environment around precision instruments. This gives a way to assess ambient parameters and their effect on instrument response. An example for Raman spectrometer is here ! doi.org/10.1002/jrs....

GitHub - ankit7540/RamanSpec_BasicOperations: Procedures (for IgorPro) to perform operations needed in day to day analysis of spectroscopic data. For example, Raman or infrared spectra where the data ... Procedures (for IgorPro) to perform operations needed in day to day analysis of spectroscopic data. For example, Raman or infrared spectra where the data is structured as array of 1-D or 2-D waves....

During graduate research, I developed procedures to automate data analysis workflows for vibrational spectroscopy, written for IgorPro. Check this github repo:

github.com/ankit7540/Ra...

Checkout my personal blog on Raman spectroscopy and associated research!

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