Raman and IR spectroscopy

In summary, Raman spectroscopy is a technique used to identify and analyze chemical compounds by measuring the scattered light from a laser shining on a sample. It differs from IR spectroscopy, which measures light absorption, and is commonly used in scientific research for its non-destructive nature, sensitivity, and ability to analyze samples in various states. However, it may have limitations with certain types of compounds and fluorescence interference.
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Homework Statement


For (NO)2+, experiments show 1 Raman active vibrational mode around 1450/cm; 2 strong IR active modes at 2400/cm and 550/cm; and 1 weak IR active mode around 3600/cm. What does that say about its geometry?




The Attempt at a Solution


Never mind, I think I got it :)
 
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Out of curiosity, what kind of mode does the weak IR active line correspond to?

The first 3 are clearly the symmetric stretch, asymmetric stretch and symmetric bend (in that order). That there are 4 modes suggests that the ion is linear, as indeed NO2^+ is. What is the fourth vibrational mode?
 

1. What is Raman spectroscopy and how does it work?

Raman spectroscopy is a technique used to identify and analyze various chemical compounds. It works by shining a laser light onto a sample, which causes the molecules to vibrate and scatter light at different wavelengths. The scattered light is then measured and compared to a reference spectrum to determine the composition of the sample.

2. What is the difference between Raman and IR spectroscopy?

Both Raman and IR spectroscopy are used to analyze the molecular structure of a sample, but they work in different ways. While Raman spectroscopy measures the scattered light, IR spectroscopy measures the absorption of infrared light by the sample. This means that Raman spectroscopy is better at identifying compounds with symmetric molecular structures, while IR spectroscopy is better at identifying compounds with asymmetric molecular structures.

3. How is Raman spectroscopy used in scientific research?

Raman spectroscopy is used in a wide range of scientific research fields, such as chemistry, biology, and materials science. It can be used to identify and analyze various compounds and materials, including proteins, polymers, minerals, and pharmaceuticals. Raman spectroscopy is also commonly used in quality control and forensic analysis.

4. What are the advantages of using Raman spectroscopy?

Raman spectroscopy has several advantages compared to other analytical techniques. It is non-destructive, meaning the sample does not need to be altered or destroyed in order to be analyzed. It is also a fast and sensitive technique, capable of detecting even small amounts of a compound in a sample. Additionally, Raman spectroscopy can be used to analyze samples in various physical states, such as solids, liquids, and gases.

5. Are there any limitations to Raman spectroscopy?

While Raman spectroscopy is a powerful analytical tool, it does have some limitations. It is not suitable for analyzing compounds that do not have polarizable bonds, such as noble gases. Additionally, fluorescence from certain compounds can interfere with the Raman signal, making it difficult to accurately analyze the sample. However, these limitations can often be overcome by using complementary analytical techniques in conjunction with Raman spectroscopy.

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