What is the principle of microwave spectroscopy?

Answer 1

Priciple of N.M.R is based upon the spin of nuclei in an external magnetic field.In absence of magnetic field,the nuclear spins are oriented randomly.Once a strong magnetic field is applied they reorient their spins i.e aligned with the field or against the field.Orientation parellel to alignment of applied force is lower in energy.When nuclei are irradiated with RF radiation the lower energy nuclei flip to high state and nuclei said to be in resonance,hence the term nuclear magnetic resonance.

Answer 2

Flame atomic absorption spectroscopy (FAAS) is a very common technique for detecting metals and metalloids in solid and aqueous samples. It is very reliable and simple to use. The technique is based on the fact that ground state metals absorb light at specific wavelenths. Metal ions in a solution are converted to atomic state by means of a flame. Light of the appropriate wavelength is supplied and the amount of light absorbed can be measured against a standard curve. The technique of (FAAS) requires a liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as acetylene and air or acetylene and nitrous oxide. The mixture is ignited in a flame whose temperature ranges from 2100 to 2800 oC. During combustion, atoms of the element of interest in the sample are reduced to free, unexcited ground state atoms, which absorb light at characteristic wavelengths. The characteristic wavelengths are element specific and accurate to 0.01-0.1nm. To provide element specific wavelengths, a light beam from a lamp whose cathode is made of the element being determined is passed through the flame. A device such as a photonmultiplier can detect the amount of reduction of the light intensity due to absorption by the analyte, and this can be directly related to the amount of the element in the sample.

Answer 3

IR radiation does not have enough energy to induce electronic transitions as seen with UV. Absorption of IR is restricted to compounds with small energy differences in the possible vibrational and rotational states.

For a molecule to absorb IR, the vibrations or rotations within a molecule must cause a net change in the dipole moment of the molecule. The alternating electrical field of the radiation (remember that electromagnetic radation consists of an oscillating electrical field and an oscillating magnetic field, perpendicular to each other) interacts with fluctuations in the dipole moment of the molecule. If the frequency of the radiation matches the vibrational frequency of the molecule then radiation will be absorbed, causing a change in the amplitude of molecular vibration.

Spectroscopy is the study of the interaction between radiation (electromagnetic radiation, or light, as well as particle radiation) and matter. Spectrometry is the measurement of these interactions and an instrument which performs such measurements is a spectrometer or spectrograph. A plot of the interaction is referred to as a spectrum.

Answer 4

Mass Spectroscopy:

The paper gave a comprehensive overview on Mass Spectroscopy. The paper discussed the

principles of mass spectroscopy, techniques and its application in the field of pesticides. Because

of high sensitivity of the techniques, mass spectroscopy has become the powerful analytical tool

for monitoring environmental pollutants, pesticides residues in food, water and soil upto parts

per billion and/or trillion levels.

Answer 5

Microwave spectroscopy is a method in which the difference in rotational energy levels of a molecule are determined. It is called microwave spectroscopy because oftentimes, the wavelength of the electromagnetic radiation (EMR) is in the micro scale (1x10-6m to 1x10-3m) and can only be conducted effectively on samples that are in a gaseous phase. There are two types of microwave spectroscopy: emission and absorbance.

Emission spectroscopy refers to measuring the EMR that is released from the molecule when it returns to its ground state from an excited state. In microwave spectroscopy, the molecule interacts with light and begins to rotate more quickly as a result. This state is usually less stable than a slower rotational energy level, so it quickly relapses to its slower state. In the process, it emits the same wavelength of EMR that it absorbed previously. In order to avoid measuring both the emitted EMR and the EMR from the source, the detector is set at a 90 degree angle from the source beam.

Absorbance/transmission spectroscopy takes a different approach. The sample is set directly between the EMR source and the detector. The wavelengths of EMR that do not interact with the sample are measured, which allows one to easily find the wavelength of EMR that does interact with the sample (and thus, the energy differences between the rotational states of the molecule).

Answer 6

Spectroscopy is the study of interaction of matter with radiation energy. Matter can result in absorption, emission, transmission, interference of the electromagnetic radiation. Different types of spectroscopy utilize different phenomenon. For example, ultraviolet spectroscopy utilizes absorption.

Answer 7

atoms vibrate at particular frequencies, depending on their energy. If the energy of a particular atom has a vibration frequency in the microwave domain then you can know it's energy by measuring it's frequency by, Energy = plank's constant (times) frequency => E=h*f

In spectroscopy matter interacts with electromagnetic waves which are classified on the basis of their frequencies. e,g ultraviolet, infra red, x rays, radio waves and microwaves. Each category brings out specific changes in the molecule like in UV electronic transitions are observed and in IR vibrational changes are observed. These changes are observed when the energy requirement of the compound matches with the energy of the wave which can be calculated by the formula mentioned above.

Answer 8

Itneraction of microwaves with polar molecule causes change orientation,due to this, rotational energy will be absorb or emit and give rotational spectra

Answer 9

The priciple of atomic absorption spectroscopy is the absorbtion of light by atoms in a gaseous state; the concentration of an element depends on the absorbance.