. After reflection of the two beams, they recombine at the beam-splitter. Depending on the location of the moving mirror, difference in the optic paths are generated. The two beams interfere constructively and therefore lead to a maximum detector response when they are in phase with each other. The beams interfere destructively when they are out of phase with each other. (14)(15) Figure 1.3 – Schematic representation of the operation of a FTIR spectrometer equipped with a Michelson interferometer. The interferogram obtained from a monochromatic source is illustrated (John 2006 (15)).
Raman spectroscopy
Raman spectroscopy is, besides IR spectroscopy, one of the two spectroscopic methods used for vibrational analysis. Both techniques are used to provide a fingerprint of molecules by generating spectra. The main difference is that IR spectroscopy is based on absorption of photons with a frequency equal to the vibrational frequency of functional groups, whereas Raman spectroscopy is based on inelastic scattering of monochromatic light. (14) Also different selection rules apply on these techniques, meaning the techniques are
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The area under the curve represents the energy required to compensate for the thermal events of the sample. Some instruments represent endothermic processes (melting) as downward curves and exothermic processes (crystallisation) as upwards peaks, while other instruments show it in the opposite way. (18) DSC can be used to evaluate different thermal events including melting, solid-state transitions, crystallization, glass transitions … (19) DSC may therefore be used to differentiate between polymorphs according to their melting point or to examine the transformation of metastable systems. It is essential though to confirm the results of DSC with other characterization techniques such as Raman spectroscopy, IR spectroscopy and X-ray diffraction.
The nano-thermal analysis method is capable of studying the specific regions of a sample irrespective of its composition. In a multi-component sample, the analysis methods make it possible for the researchers to distinguish between the different components and identify the different characteristics found in each of the sample (Craig, 2002). During the analysis of any sample, the nano-thermal method does not necessarily require the physical alteration of the sample. In its place, it is capable of analyzing any sample through surface studies.
TLC allows identification of compounds based on polarity. Nonpolar compounds move higher up on the TLC plate than polar compounds because polar compounds are more attracted t...
Every chemical element or compound have specific properties that make them different than the other. However, these properties help us to understand every element or compound in which they can be used and how we can deal with them. These properties can be chemical properties which are defined as "that property must lead to a change in the substances ' chemical structure", such as heat of combustion and flammability ("Physical and Chemical…"). Also, these properties can be physical properties which are defined as the properties "that can be measured or observed without changing the chemical nature of the substance", such as mass, volume, boiling and freezing points ("Physical and Chemical…"). These two properties are related to each other. For
The expected melting point of Semicarbazone of Cyclohexanone is 166°C.1 The assumed product is Semicarbazone of Cyclohexanone. Observed temperature being lower than the expected may indicate a contamination or an impurity. The low temperature result was shown to be more accurate than the room temperature result. Perhaps, in the room temperature, there was more of a mix in the products (i.e. containing both Semicarbazone of Cyclohexanone and Furaldehyde). This is reinforced by the pale yellow colour observed, when Semicarbazone of Cyclohexanone is supposed to be white. Room temperature result could be close to the eutectic point. This is kinetic control, as it is formed much quicker than the product of the high temperature reaction. To fix the problem of lower than expected melting point could be have a set temperature as to how cold the low temperature should be (e.g.
The objective of this experiment was to identify a metal based on its specific heat using calorimetry. The unknown metals specific heat was measured in two different settings, room temperature water and cold water. Using two different temperatures of water would prove that the specific heat remained constant. The heated metal was placed into the two different water temperatures during two separate trials, and then the measurements were recorded. Through the measurements taken and plugged into the equation, two specific heats were found. Taking the two specific heats and averaging them, it was then that
Before you can observe with a Newtonian reflector telescope, you need to align or collimate its optical parts. The goal of collimation is to insure that both the primary and secondary mirrors as well as the eyepiece are correctly lined up to give clear, sharp views.
At very low supersaturation levels, say less than a few percent relative to ice, crystals grow mostly as simple hexagonal prisms. The aspect ratio (ratio of sizes along the a-axis and c-axis) varies somewhat with temperature at low supersaturation, changing from plates (-2 C) to columns (-5 C) to plates (-15 C) and back to columns again (-30 C).
Connect oscilloscope to amplifier. Modulate laser as before. Point laser towards photo detector. Perform measurements of voltage output for different frequencies. Take
1.9.1: Melting point51- A pure crystalline organic compound has a definite and sharp melting point, that is, the melting point range (the difference between the temperature at which the sample collapse or at which the sample becomes completely liquid) does not exceed above 0.5oC. If any miscible or partially miscible impurities are present in small quantity it will increase the melting point range and cause the initiation the melting to occur at a temperature lower than the melting point of the pure substance. The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exists in equilibrium. The melting point of substance depends on pressure and is usually specified at standard pressure. But when temperature is reverse changes from liquid to solid, it is referred to as the freezing point or crystallization point.
VITIS/ Visible and Infrared Thermal Imaging Spectrometer: its purpose is to assess the component of the solids in the nucleus as well as the various gases found in the coma of the comet (the next layer after the nucleus);
The plasma consists of electronically excited atoms and ions, which can then be analyzed by the spectrometer. When the laser pulse terminates, the plasma begins to cool [11]. It is during this cooling process, where the electrons of the atoms and ions at the excited states decay back into their natural ground states, causing the plasma to emit characteristic wavelengths of light. The atomic emissions can be detected approximately 1 μs after the initial pulse. The emitted light from the plasma is collected by the spectrometer coupled with either a CCD or ICCD spectrograph detector module for the LIBS spectral analysis [11]. Each element correlates to a unique LIBS spectral peaks. Thus, by identifying the different peaks of the analyzed sample, its chemical composition can be rapidly
V. Amarnath, D. C. Anthony, K. Amarnath, W. M. Valentine, L. A. Wetterau, D. G. J. Org. Chem. 1991, 56, p. 6924-6931.
The Michelson interferometer is a device that can divide a beam of radiation into two paths and then recombine the two beams after a path difference has been introduced. A condition is thereby created under which interference between the beams can occur. The variation of intensity of the beam emerging from the interferometer is measured as a function of path difference by a detector. The Michelson interferometer consists of two mutually perpendicular plane mirrors, one of which can move along an axis that is perpendicular to its plane.
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
A Spectrophotometer is employed to measure the amount of light that a sample absorbed. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector. A Spectrophotometer consists of two instruments; one is a Spectrometer used for producing light of any selected color (wavelength) and second is a Photometer used for measuring the intensity of light.