Spectroscopy Flashcards
What is spectroscopy?
Science of dealing with the way matter interacts with different types of EMR
T/F EMR that has a high energy also has a high frequency and a short wavelength
True
An _____________ _________ shows different types of EMR radiation ranked by wavelength, frequency, and energy.
EMR spectrum
What are the 3 types of light commonly used by spectroscopic analyzers?
UV, IR, Visible
What light contains all the wavelengths of EMR in the visible region?
White light
The light that passes through a transparent material in the visible region is ____________ light.
Transmitted
What are the 2 types of EMR emission used as a radiation source?
Continuous emission: generated by a hot solid object
Line emission: generated by an energized vapour as discrete wavelengths of light
A special type of device called an _________ filter is commonly used in process photometric analyzers to pass the desired wavelength
Interference
What type of cell window can be used in UV, IR, and visible photometric analyzers?
Sapphire
What is flourescence?
Emission of lower energy EMR from a substance that absorbs higher energy radiation
The electrons in molecules and atoms normally exist with low energy levels known as ____________ states.
Ground
What is absorption?
Removal of energy from incident light by chemicals in the path
What happens when broadband EMR is transmitted through a gas sample?
The gas sample absorbs only some specific wavelengths of EMR, this results in an absorption spectrum that can be used to identify the gas (fingerprinting)
What is one of the conditions to make Beer-Lambert’s law valid?
The EMR used for measurement has to be monochromatic (single wavelength)
What are the 3 types of wavelength selectors (monochromators)?
1) Interference filter
2) Prizm
3) Diffraction grating
What is a typical cell length size for a liquid sample?
Less than 1 cm
What is a typical cell length size for a gas sample?
Can be as large as several meters
What are the three types of EMR detectors commonly used for UV and visible?
1) Photodiode
2) Phototube
3) Photomultiplier tube
What are the 2 categories with examples of IR detectors?
1) Thermal: thermopile, thermocouple
2) Photo detector: photovoltaic detector, photoconductive detector
What type of noise is known to affect PMT sensors and how is this avoided by the
analyzer design?
Thermal electrical noise; mitigated by cooling the sensor below room temperature
