From the nm spectrum data, a continuum tail was observed towards the end of the spectrum at longer wavelengths. Hence, the signal of background radiation will be subtracted from cell B. The absorption spectrum of iodine yields information about the excited state B. However, each additional term would have a smaller contribution to the overall accuracy of the data. Lab Report on The electronic absorption spectrum of iodine in lab reports The lab report below was submitted as part of the coursework for CM Principles of Spectroscopy. Electronic transitions can occur between populated vibrational states of the ground state and various vibrational states of the excited states. One of the most interesting aspects of quantum transitions that are revealed by the Morse Potential Curve is the fact that the anharmonicity character of the system is considerably more in the excited state than it is in the ground state. Search my Subject Specializations:

Romance of the two wisdom teeth Romance of the two wisdom teeth. At higher wavelengths, the energy that the molecule absorbs is much lower. Skip to main content. Do note that my report is well-circulated online and many of my juniors have received soft copies of it. Furthermore, gas molecules are much less closely packed than a liquid sample. Haikus on Technology Orchids Wild?

University Press Scholarship Online. Phosphorescence of iodine can occur when two excited states of different total spin have comparable energies. Since the internuclear distance does not change during the absorption of a photon, the transition is drawn with a vertical line on the potential energy diagram. Actually, adding more terms would definitely increase the accuracy.


By then, noise dominates and peaks are harder to distinguish. I odine crystals sublimes easily even at room temperature because of its high vapour pressure.

Thus iodine crystals sublime easily at room temperature. Descriptions of and reasons behind the electronic absorption spectrum of iodine.

Enter the email address you signed up with and we’ll email you a reset link. This information is valuable since such molecules may only exist in such unstable, excited states for a very short time. The literature values of D 0 and D e are and cm -1 respectively.


Log In Sign Up.

Birge–Sponer method

The sides of the gas cell was also not touched as fingerprint markings will scatter the light passing through, thus affecting the transmittance readings. Peak Number from spectrum.

Sample calculation for determining wavenumber: In accordance with Boltzmann distributions, no higher transitions can be visible at this temperature. Information regarding the maximum intensity transitions as well as vibrational wave functions can also be obtained but will not be discussed in this study. To obtain those values, two analytical models were used: This results in a very low iodine concentration.

Singlet-triplet transition is possible iocine spin-orbit coupling occurs because iodine is a heavy molecule.

This means that the energies form a continuum rather than being quantized. The dissociated I virge molecule can take up any amount of kinetic energy, meaning that the transitions which occur are no longer quantised and thus a continuum tail results.

Not only is it less laborious and more intuitive, automatically provides necessary means to analyze the error in the data. One of the main sources of error in this experiment is incorrect assignment of peaks.

Thus, the absorbance of iodine recorded will only belong to the gaseous iodine, excluding the background radiation. This continuum tail arises due to birgr dissociation of the I 2 sponed.

However, under conditions of this experiment low resolutionthe rotational peaks within each band are resolved and the distinction between the vibrational and rotational bands is, for the purposes of this experiment, may be ignored. The Morse Potential Curve also provides a wealth of information regarding the Bireg molecule and its different characteristics can be determined. Classical, Early, and Medieval Prose and Writers: An iodine crystal was placed inside a 10 cm gas cell and vaporized using a water bath.

These errors would have a great impact on the obtained values of I2 and the Morse Potential curve. Since the rotation constant, B, is inversely proportion to the square of r i. Lab Report on The electronic absorption spectrum o A longer path length will result in more iodine molecules undergoing electronic excitations.

Hence, subtracting the background noise ensures that the spectra recorded belongs to sample and gives a better resolution and clarity of spectrum. Thus, I 2 only has 1 normal vibrational mode. Thus, this limits the accuracy of experimental values obtained. Thus, the frequency of incident beam radiated by spectrophotometer should not reach and exceed this value as iodine will then dissociate and the spectrum obtained will be a continuum plot.


This causes the rotation line peak separation under a vibration line to be separated by a larger B constant, resulting in the broadening of the band. Most importantly, a linear regression analysis of the data provides more accurate results as shown in Table 2. Assigning these peaks their respective transitions can then be analyzed computationally to solve equation 1.

Lab Report on The electronic absorption spectrum of iodine | Artxy

After a molecule has undergone an electronic transition iodone an dponer state, there are several ways by which its excess energy may be lost. In this experiment, we analyze the electronic spectrum of I2 gas to extract a tremendous amount of data regarding the energetics and properties of the molecule.

Thus, there are 2 unpaired electrons in B. Print Save Cite Email Share. Table 2 also illustrates a summary of relations for each variable.

Please, subscribe or login to access full text content. In order to ensure that the assignments are consistent, the results from the overlapping region — By spin selection rule, transition from triplet to singlet state is forbidden. Publications Pages Publications Pages. Wavelength of peaks from spectrum obtained are matched with the This characteristic explains the fact that the transitions between higher vibrational levels are smaller and provides insight to the maximal vibronic transitions beyond which the molecule dissociates into atoms.

The spin multiplicity in B is 3, total spin angular momentum is 1. The concept of transitional levels and its origin in various quantum mechanical theories has been explored and proven by various spectroscopic and theoretical experiments.

Author: admin