Spectroscopic notation

Optically active cations generally encompass the transition metal series of the periodic table. Atoms or ions with closed electron shells are not optically active, that is- they do not interact with photons having energies lower than about 5.00 ev. Examples of closed shell ions are  

On the other hand, optically active ions have electrons external to the closed shells which can be excited by a photon of proper energy. Examples are  

Note that Sn2+ is optically active whereas Sn + is not. In order to describe the energy states of an optically active cation, we must turn to the field of spectroscopy. The most often used method of notation is that of Russell-Saunders terminology. 

Russell-Saunders coupling is used because it agrees with experimental values most of the time. However, there are cases where it has been found better to sum the individual j values and then sum these to give the final value. 

In Russell-Saunders coupling, sometimes called L-S coupling, the individual the spectroscopic terms are based on the L - values obtained (which are small whole numbers). The spin term is a resultant of 2S -h 1. The central term is thus defined like this  

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In this section, we briefly discuss spectroscopic consequences of the R-T coupling in tiiatomic molecules. We shall restrict ourselves to an analysis of the vibronic and spin-orbit structure, detennined by the bending vibrational quantum number o (in the usual spectroscopic notation 02) and the vibronic quantum numbers K, P. 

At this point the nomenclature used in XPS and AES should be explained. In XPS the spectroscopic notation is used, and in AES the X-ray notation. The two are equivalent, the different usage having arisen for historical reasons, but the differentiation is a convenient one. They are both based on the so-called j-j coupling scheme describing the orbital motion of an electron around an atomic nucleus, in which the... 

The old spectroscopic notation of s,p,d,f, referring to states with quantum number l = 0,1, 2,3, is still in common use. 

In an atomic term symbol the value of L = 1,2,..., etc. is coded according to spectroscopic notation as 5, P, D,F,G,... etc. (alphabetically for L > 3). Likewise, each atomic state can be characterized by a total electronic spin quantum number S,... 

In this expression we have dropped the rotational part and written only the vibrational part. We also note that the spectroscopic notation... 

This expression can be converted to the usual spectroscopic notation by introducing the local vibrational quantum numbers, v0, vb, vc of Figure 4.14. These quantum numbers are related to the group quantum numbers by... 

Using spectroscopic notation, write down the electronic configurations of the following species (note that some are ions) ... 

Consider the electronic configuration of carbon again Is 2s 2pl Remember, there are three different p orbitals in the 2p subshell the p orbital lies on the x-axis the p orbital lies on the y-axis and the p orbital lies on the z-axis. The different p orbitals are degenerate. To obey Hund s rule, these degenerate orbitals must be filled singly before spin pairing occurs. To obey the Pauli exclusion principle, when an orbital is full with two electrons, these electrons must have opposite spins. This is not shown using spectroscopic notation, but is seen when orbital box notation is used. 

The electron arrangement of potassium is given in the SQA Data Booklet as 2, 8, 8,1. In spectroscopic notation, the electronic configuration of potassium is 1s 2s 2p 3s 3p 4sL The diagram shows this information presented in orbital box notation. 

The table shows the electronic configuration in spectroscopic and orbital box notation for the elements from scandium to zinc. [Ar] represents the electronic configuration of argon, which is Is 2s 2p 3s 3p . It is okay to use this shorthand here instead of writing out the full electron shells up to 3p. However, in the exam you should write out the spectroscopic notation for each element in full. 

The electron arrangements in the SQA Data Booklet and the electronic configurations written in spectroscopic notation in the table show that chromium and copper are out of step with the aufbau principle. However, there is a special stability associated with half-filled or completely filled d orbitals. Bear this in mind when looking at the orbital box notation and you can understand why chromium is [Ar] 3d 4s and copper is [Ar] 3d 4s, rather than the [Ar] 3d 4s and [Ar] dd" 4s as you might have expected. 

A.12-1 for a brief review of atomic-spectroscopic notation). In a given term-symbol, T will be S, P, D, F, or G etc. depending on whether the total electronic orbital angular-momentum quantum number L is 0, 1,... 

The first Tour letters originate in spectroscopic notation (see page 26) and the remainder follow alphabetically. In the previous section we have seen the various angular wave functions and the resulting distribution or electrons. The nature or the angular wave Function is determined by the value or the quantum number i... 

In denoting the valence state of an element, Chemists very often use M°, M+, M2+ etc., or M°, M(I), M(H) etc. for neutral, mono and divalent ions. Spectroscopists, however, prefer to write M I, M II, M III in describing the above valence states. We have used the very first notation throughout the book with regard to chemical compounds. In this chapter spectroscopic notations are also included beside the chemical notation for the sake of clarity. 

In this article both unsensitized and mercury vapor sensitized reactions are discussed. The plan has been to proceed from the chemically simplest system, oxygen molecule, to the chemically most complex, ozone plus hydrogen peroxide. Unless otherwise stated, thermochemical values have been taken from compilations of the National Bureau of Standards (68) and are reported in kcal. for the reaction represented in mole amounts. Conversion factors for energy units, spectroscopic notation, and unless noted, spectroscopically based values have been taken from... 

Herzberg (41). The extent of spectroscopic notation used is the minimum consistent with clarity. 

Figure 2.2 Demonstration of the two equivalent nomenclatures used for the description of inner-shell levels and X-ray transitions (also Auger transitions, see below). The vertical direction is regarded as the energy axis (but is not to scale here). On the left-hand side is given the notation which is frequently used in inner-shell spectroscopy, on the right-hand side the corresponding single-orbital quantum numbers with n, t and j being, respectively, the principal quantum number, the orbital angular momentum and the total angular momentum which includes the spin of the electron. Also shown are the main X-ray transitions with their spectroscopic notation (for a more complete plot which includes...

Fig. 12.6. Measured (full circles) and calculated (open circles) linewidths fir for He HF(j = 1) as a function of the total angular momentum J for helicity states fi = 0 and 1 and even parity. The corresponding spectroscopic notation is e and ITe, respectively. 1000 MHz corresponds to 0.033 cm-1. Adapted from Lovejoy and Nesbitt (1990).

Gas Metastable energy (eV) Ionization potential (eV) Spectroscopic notation... 

The term J(J+ l)h2/2/xr2 in equation (1) is typically very small compared with the other terms, for small values of J, and may be regarded as a perturbation on the vibrational levels, owing to rotational motion. In spectroscopic notation, the correction due to this term is often labelled F(J). 

D. RUSSKLL-SAUNDERS COUPLING, SPECTROSCOPIC NOTATION, AND MULTIPLICITY... 

This compilation covers all molecular lines detected by radioastronomical techniques in the interstellar medium. The listing includes all lines reported up to August 1973. The spectroscopic notation corresponds to the one used in Table 6. The electronic ground state is indicated only in cases where it is different from a 12 state. Each entry under the six sources listed means that this particular transition has been observed in that source. 

Here and below we follow the usual spectroscopic notations for molecular terms [8, 9], In the case of the Hund coupling scheme a the notation a +1Aw refers to a molecular term with total electron spin S, the projection A (A > 0) of electronic orbital angular momentum on the molecular axis, and parity w. 

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