Raman Vs FTIR Flashcards
What does Raman spectroscopy use to analyze substances?
A laser to measure molecular vibrations via scattered light.
What type of scattering does Raman measure?
Inelastic scattering (Raman scattering).
Fill in the blank: Raman spectroscopy works by analyzing the energy shift of _________ photons caused by molecular vibrations.
scattered
What is the typical laser wavelength used in the ACE-ID?
785 nm
What does ORS technology in ACE-ID do?
Spreads laser energy across the sample surface to avoid heating and improve signal clarity.
Fill in the blank: The detector in Raman spectroscopy measures the __________ spectrum, which is a molecular fingerprint.
Raman
What is Raman spectroscopy best at detecting?
Non-polar molecules and carbon-based compounds.
What is the purpose of a notch or edge filter in Raman spectroscopy?
To remove Rayleigh scattering and isolate Raman scattering.
Fill in the blank: Raman spectroscopy generates a spectrum that shows __________ intensity as a function of __________.
scattering; wavenumber
What type of sample preparation is needed for Raman spectroscopy?
None. It can analyze substances without preparation.
What kinds of materials can Raman struggle with?
Fluorescent or dark materials (they interfere with the laser signal).
What detector is used in the ACE-ID for Raman scattering?
A CCD detector (Charge-Coupled Device).
Fill in the blank: Raman spectroscopy is based on light interacting with the __________ of a molecule.
vibrations
Why is Raman suitable for hazmat scenarios?
It allows for non-contact analysis through clear containers, reducing exposure.
Why is the ACE-ID safer for explosive materials?
It uses Orbital Raster Scan (ORS) to reduce laser heating on the sample.
What does FTIR stand for?
Fourier Transform Infrared Spectroscopy.
What kind of light does FTIR use?
Infrared light from a broad-spectrum source.
What does FTIR measure?
The absorption of infrared light by molecular bonds.
Fill in the blank: FTIR uses a __________ to split and recombine IR beams, creating an interference pattern.
Michelson interferometer
What is the primary material used for the ATR crystal in the HazMatID Elite?
Diamond.
What type of molecular bonds is FTIR best at detecting?
Polar bonds (e.g., O-H, C=O).
Fill in the blank: The ATR crystal creates an __________ wave that penetrates the sample to analyze its molecular vibrations.
evanescent
What does the interferometer in FTIR do?
It splits the IR beam into two paths and recombines them to create an interference pattern.
What is the role of the Fourier Transform in FTIR?
Converts the interference pattern into a usable IR spectrum.
Fill in the blank: FTIR spectroscopy shows how molecules absorb __________ radiation at specific __________.
infrared; wavenumbers
What limits FTIR in hazmat response?
It requires direct contact with the sample, which may pose risks with toxic or reactive substances.
What types of materials can the HazMatID Elite analyze?
Solids, liquids, and powders.
Why is a diamond ATR crystal used in HazMatID Elite?
Diamond is hard, durable, and has a high refractive index for efficient IR analysis.
What is the wavelength range typically analyzed by FTIR?
4000–400 cm⁻¹ (mid-infrared region).
Fill in the blank: The HazMatID Elite can identify up to __________ substances from its built-in library.
10,000
Which method can analyze through glass or plastic containers?
Raman (ACE-ID).
Which method requires direct contact with the sample?
FTIR (HazMatID Elite).
Fill in the blank: Raman spectroscopy uses __________ scattering, while FTIR measures __________ of IR radiation.
inelastic; absorption
Which method works better for non-polar molecules?
Raman.
Which method is better for identifying chemical warfare agents?
FTIR (HazMatID Elite).
Why is Raman limited for polar molecules?
Polar bonds have weak Raman scattering signals.
What is the common detector material used in FTIR devices?
Pyroelectric or MCT (Mercury Cadmium Telluride).
Fill in the blank: Raman spectroscopy works best with __________ samples, while FTIR requires __________ samples.
transparent; direct contact
What makes Raman and FTIR complementary in hazmat?
Raman is non-contact and fast, while FTIR provides a broader chemical library and better sensitivity to polar compounds.
Fill in the blank: The ACE-ID’s laser wavelength is __________ nm, while FTIR uses __________ wavelengths.
785; infrared (4000–400 cm⁻¹)
Why is a spectral library critical for both Raman and FTIR?
The library allows for identification of substances by comparing measured spectra to known chemical fingerprints.
Fill in the blank: Raman spectroscopy detects changes in __________ energy, while FTIR measures __________ energy absorbed by molecules.
scattered; infrared
Why is a spectral library critical for both Raman and FTIR?
It allows substances to be identified by matching measured spectra to known fingerprints.
Fill in the blank: FTIR works best for __________ bonds like O-H, while Raman works better for __________ bonds like C-H.
polar; nonpolar
Which tool uses a CCD detector and which uses pyroelectric?
Raman: CCD; FTIR: Pyroelectric.
What is the detector setup for Raman spectroscopy?
Laser energy and light-scattering vibrations measure non-polar bonds.
What is the range of wavelengths used in FTIR?
4000–400 cm⁻¹.
Why is FTIR effective for liquid and solid identification?
The ATR crystal ensures direct molecular interaction with IR light.
Which spectroscopy works better through containers?
Raman (ACE-ID).
Fill in the blank: The Raman spectrum measures __________ intensity, while FTIR shows __________ absorption.
scattering; infrared
What is Raman Spectroscopy?
A technique where a laser shines a single color of light onto a material to identify it.
What happens to most of the light in Raman Spectroscopy?
Most of the light bounces back unchanged (Rayleigh scattering).
What is Raman scattering?
A small part of the light interacts with the material’s molecules and shifts in energy.
Why do energy shifts occur in Raman Spectroscopy?
Because the laser interacts with the vibrations of the chemical bonds in the molecules.
What is a Raman spectrum?
The resulting pattern of shifted light, unique to the material, like a fingerprint.
How does a device identify a material using Raman Spectroscopy?
By comparing the Raman spectrum to a library.
What is FTIR Spectroscopy?
A technique where infrared light is directed at a material to identify it.
What do molecules in FTIR Spectroscopy do?
They absorb specific wavelengths of infrared light depending on their chemical bonds.
What is an IR spectrum?
A unique pattern showing which parts of the infrared light were absorbed.
What is the role of the ATR crystal in FTIR?
To ensure the material is in good contact with the infrared light, especially for solids and liquids.
How does a device identify a material using FTIR Spectroscopy?
By comparing the IR spectrum to a library.
What is the main difference between Raman and FTIR Spectroscopy?
Raman looks at scattered light caused by molecular vibrations, while FTIR looks at absorbed infrared light.
What are non-polar molecules?
Molecules with no significant charge difference across their bonds
Non-polar molecules do not have regions of partial positive or negative charge.
What type of bonds are found in non-polar molecules?
Symmetrical bonds (e.g., C-H, C=C)
Symmetrical bonds allow for equal sharing of electrons.
Fill in the blank: Non-polar molecules often have __________ bonds that share electrons equally.
symmetrical
Are non-polar molecules typically carbon-based or non-carbon-based?
Often carbon-based (e.g., hydrocarbons)
Hydrocarbons are compounds consisting solely of hydrogen and carbon.
Give an example of a non-polar molecule.
Methane (CH₄) or benzene (C₆H₆)
Both methane and benzene are commonly referenced non-polar molecules.
What are polar molecules?
Molecules with uneven charge distribution due to differences in electronegativity
This uneven distribution creates regions of partial charges.
What type of bonds are found in polar molecules?
Asymmetrical bonds (e.g., O-H, C=O)
Asymmetrical bonds result in unequal sharing of electrons.
Fill in the blank: Polar molecules have __________ bonds where electrons are shared unequally.
asymmetrical
Are polar molecules typically carbon-based or non-carbon-based?
Can be both (e.g., alcohols for carbon-based; water for non-carbon-based)
Alcohols contain carbon and can exhibit polar characteristics.
Give an example of a polar molecule.
Water (H₂O) or ethanol (C₂H₅OH)
Both water and ethanol are commonly studied polar molecules.
What are carbon-based molecules?
Molecules primarily made of carbon and hydrogen atoms
Carbon-based molecules form the backbone of organic chemistry.
Are carbon-based molecules usually polar or non-polar?
Often non-polar (e.g., hydrocarbons) but can be polar if functional groups are present (e.g., alcohols)
The presence of functional groups can alter the polarity of carbon-based molecules.
Fill in the blank: Carbon-based molecules like hydrocarbons are mostly __________, but adding O-H or C=O groups makes them __________.
non-polar; polar
Give an example of a carbon-based molecule.
Methane (CH₄) or ethanol (C₂H₅OH)
Methane is a simple hydrocarbon, while ethanol includes a polar functional group.
What are non-carbon-based molecules?
Molecules that do not primarily consist of carbon atoms
Non-carbon-based molecules may include various inorganic compounds.
Are non-carbon-based molecules usually polar or non-polar?
Often polar (e.g., water, ammonia)
Non-carbon-based molecules tend to have polar characteristics due to their molecular structure.
Fill in the blank: Non-carbon-based molecules like water are typically __________ due to their asymmetrical bonds.
polar
Give an example of a non-carbon-based molecule.
Water (H₂O) or ammonia (NH₃)
Both water and ammonia are widely recognized as non-carbon-based polar molecules.
