Rotational and Vibrational Spectra

Purely rotational transitions of PH and PD, generated in microwave discharge flow systems by reacting phosphorus vapor with H or D atoms, have been observed by laser magnetic resonance (LMR) in the far IR. Using magnetic fields up to 1.4 T and eleven laser lines between 

The analyses of these LMR spectra included investigations into the effects of rotation, centrifugal distortion, and fine-structure interaction. The results led to very precise values for the respective molecular constants (see pp. 12, 15/7) [1 to 3]. 

The fundamental absorption band of PH in its ground state X was observed at high resolution using a tunable diode laser spectrometer eighteen lines betwen 2224.4125 and 2107.8160 cm (4.50 to 4.74 pm) have been identified as P-branch transitions with N = 3 to 7 and 9, where each transition exhibits the fine-structure triplet splitting due to AJ = AN transitions between the three sublevels (J = N +1, N, N -1) of the respective rotational levels N and N. Two further lines at 2292.1918 and 2308.1542 cm (-4.3 pm) have been identified as the R-branch transitions with N , J = 0,1 and 1,0. Hyperfine splitting could not be resolved. The analysis, which included rotational and centrifugal distortion effects as well as spin-spin 

For PD in the electronic ground state (D atoms from MW discharges through DgO or Dg pumped over red phosphorus), rovibrational transitions have been detected by LMR. Measurements in fields of 0.2 to 1.9 T and using seven laser lines around 6 pm in perpendicular 

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Non-rigidity has important consequences for the rotation and vibration spectra. Extensive experimental investigations exist in this domain they are based on the elaboration of model hamiltonians to describe the external motions. Recently, non-rigid molecule effects on the rovi-bronic levels of PF5 have been examined , so leading to the prediction of the spectroscopic consequences of Berry processes. 

See introductory remarks in Section I.A.4 of Chapter 7. The IR vibration frequencies of compounds MH4 and MeMH3 were calculated ab initio for the metallic elements of group 14, including M = Sn, and compared with experimental data from various sources105. Many parameters pertaining to rotational and vibrational spectra of compounds... 

In this way the study of spectra gives even more detailed information than the consideration of specific heats. It is found that infra-red rotation and vibration spectra are only given by those molecules, such as HC1, which are composed of a negative and a positive portion. Strictly homo-polar molecules do not absorb in the infra-red, although the theory of specific heats, and the analysis of the visible spectrum, leave no doubt about the existence of... 

The molecular structure of gaseous tetrahydropyran has been determined by electron diffraction the dimensions are presented in Figure 7 (79ACS(A)225). The molecule exists in the chair form with Cs symmetry consistent with the conclusions based on NMR, rotational and vibrational spectra. The torsional angles suggest that the heteroatom causes no flattening of the ring relative to that of cyclohexane. 

Figures 2.3a,b show the model of Bernal and Fowler (1933) for the water molecule. The molecular geometry is well known (Benedict et al 1956) from rotational and vibrational spectra. The oxygen atom has eight electrons, and has the electronic configuration ls22s22p4. Each hydrogen atom has a Is1 electron these electrons are shared with two bonding electrons of oxygen, to constitute the water molecule.

The observation, evaluation, and interpretation of rotational and vibrational spectra at low or high temperature yields additional information in different fields of physical chemistry, as described by Flerzberg (1945, 1950) Wilson, Decius and Cross (1955) Colthup, Daly and Wiberley (1975) Brandmiiller and Moser (1962) Volkmann (1972) Long (1977) Schrader (1980) Giinzler and Bock (1975) Orville-Thomas (1974) Irvin (1976) and Sherwood (1972). 

E.E.Nikitin, Band shapes of induced rotational and vibrational spectra of diatomic molecules, in Adv. Molec. Spectroscopy, Pergamon Press, p.298 (1962) E.E.Nikitin, Resonance and nonresonance intermoleeular energy exchange in molecular collisions, Disc.Faraday Soc. 33, 14 (1962)... 

Relate the moments of inertia, bond lengths, and vibrational force constants of diatomic molecules to their rotational and vibrational spectra (Section 20.2, Problems 5-8, 11-14). 

D. M. Dennison Rev. Mod. Phys. 3, 280 (1931). A discussion of the methods of treating the rotational and vibrational spectra of polyatomic molecules. 

MOLECULAR SPECTROSCOPY 1 ROTATIONAL AND VIBRATIONAL SPECTRA 265 The force constant, k. is assumed to be the same for both molecules. The fractional difference is... 

MOLECULAR SPECTROSCOPY 1 ROTATIONAL AND VIBRATIONAL SPECTRA 267 Xe data are usually reported as x v which is ATjU = 14.45 cm ... 

So the great advantage of conventional spontaneous Raman spectroscopy is its simplicity, with complete rotational and vibrational spectra obtainable in a single run on a simple instrument using visible optics. The disadvantages include the inherent weakness of the... 

We see in Section 8.2.1 that we can express the interaction between two bound atoms by a simple classical ( harmonic ) restoring force (Figure 2.14). Provided that we permit only small atomic displacements around the equilibrium structure then the approximation holds true, and often it allows us to simplify complex problems. This process lies at the heart of what is known as the harmonic approximation, a simplification that is exploited in computational chemistry, and in the interpretation of diffraction data and of rotational and vibrational spectra. 

Despite the fact that we treated vibrational and rotational spectroscopy first, the astute student will recognize that one of the mysteries of classical mechanics involved electronic spectroscopy. The inability to explain the (electronic) spectrum of the hydrogen atom was a major reason for the development of quantum mechanics. Yet, we have put off a detailed discussion of it until after considering rotational and vibrational spectra. 

Herman, R. M. and Ogilvie, J. F. (1998). An effective Hamiltonian to treat adiabatic and nonadiabatic effects in the rotational and vibrational spectra of diatomic molecules. Adv. Chem. Phys., 103, 187-215. 

Section 23.3 Rotational and Vibrational Spectra of Diatomic Molecules... 

Hirota E (1994) Rotational and vibrational spectra of free radicals and molecular ions. Annual Reports on thel Progress of Chemistry, Section C, Physical Chemistry 91 3 36. 

Child, M.S. and Longuet-Higgens, H.C. (1961) Studies of the (ahn-Teller effect. 111. The rotational and vibrational spectra of symmetric-top molecules in electronically degenerate states. Phil. Trans. R. Soc. Land., A 254, 259. 

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