High-resolution rotational spectroscopy

Milet A, Struniewicz C, Moszynski R, Sadlej J, Kisiel Z, Bialkowska-Jaworska E, Pszczolkowski L (2001) Structure and properties of the weakly bound trimer (H20)2HC1. Theoretical predictions and comparison with high-resolution rotational spectroscopy. Chem Phys 271 267-282... 

As we have seen elsewhere in this book, the techniques of high-resolution rotational spectroscopy are beginning to be applied to transition metal molecules, and this is particularly true of double resonance methods. We now review some of the work which has been described, again in a mainly chronological order. 

The structures of VdW dimers, considered as weakly bounded complexes in which each monomer maintains its original structure (Buckingham, 1982), are studied at low temperatures by sophisticated experimental techniques, such as far infrared spectra, high-resolution rotational spectroscopy in the microwave region, and molecular beams. Distances Re between the centres of mass and bond strengths De at the VdW minimum for some homodimers of atoms and molecules taken from Literature are collected in Table 4.4. 

The Other experimental techniques include high-resolution rotational spectroscopy and other kinds of spectroscopy. The microwave region is where the pure rotational spectra may be obtained, but the other regions that are used for various spectroscopies also have rotational structure at sufficiently high resolution. This is for the determination of metrical aspects of structure. The scope of techniques that yield information on molecular shape and symmetry is much broader. One of the other techniques is computations that have become popular not only as being applied on their own, but also as part of such concerted structure analysis. 

Even if not directly observable, intermolecular forces influence the microscopic and bulk properties of matter, being responsible for a variety of interesting phenomena such as the equilibrium and transport properties of real fluids, the structure and properties of liquids and molecular crystals, the structure and binding of Van der Waals (VdW) molecules (which can be observed under high resolution rotational spectroscopy [5-8] or molecular beam electric resonance spectroscopy [9]), the shape of reaction paths and the structure of transition states determining chemical reactions [10]. 

Asvany O, Ricken O, Muller HSP, Wiedner MC, Giesen TF, Schlemmer S (2008) High-resolution rotational spectroscopy in a cold ion trap H2D and D2H. Phys Rev Lett 100 233004... 

A very significant example that allows to stress the predictive capabilities of quantum chemistry in the field of high-resolution rotational spectroscopy is provided by recent analysis and assignment of the hyperfine structure of the rotational spectrum for [80]. Without going into details, we commit to Figure 6.6 the conclusions. To summarize, the analysis of the recorded hyperfine structure in the rotational spectrum of H2 0 was hampered by the great complexity of the hyperfine strucmre itself. In the present case, the hyperfine stracmre resulted to be particularly crowded... 

Figure 5.17 shows the rotational Raman spectrum of N2 obtained with 476.5 nm radiation from an argon ion laser. From this spectrum a very accurate value for Bq of 1.857 672 0.000 027 cm has been obtained from which a value for the bond length tq of 1.099 985 0.000 010 A results. Such accuracy is typical of high-resolution rotational Raman spectroscopy. 

Vibrational transitions accompanying an electronic transition are referred to as vibronic transitions. These vibronic transitions, with their accompanying rotational or, strictly, rovibronic transitions, give rise to bands in the spectrum, and the set of bands associated with a single electronic transition is called an electronic band system. This terminology is usually adhered to in high-resolution electronic spectroscopy but, in low-resolution work, particularly in the liquid phase, vibrational structure may not be resolved and the whole band system is often referred to as an electronic band. 

Microwave spectroscopy is generally defined as the high-resolution absorption spectroscopy of molecular rotational transitions in the gas phase. Microwave spectroscopy observes the transitions between the quantised rotational sublevels of a given vibrational state in the electronic ground state of free molecules. Molecular... 

Stoicheff, B. P. High resolution Raman spectroscopy of gases. X. Rotational... 

One of the most important aims of our theoretical work is to assist in the interpretation and understanding of high-resolution molecular spectroscopy experiments. We have already been able [1] to provide assistance of this kind in that, with our calculated values for the rotational energies in the 4v2 vibrational state of we could verify (and, for a few transitions, refute) the tentative... 

High-resolution Raman spectroscopy of gases with different He-Ne and Ar laser lines was also performed by Weber etal. The authors determined relative scattering cross-sections for the pure rotational Raman spectrum of Oj. 

A coirplete understanding of the role of carbohydrates in biological systems requires knowledge of the distribution at equilibrium of the various conformers in aqueous solution. The conformational behavior of carbohydrates in solution can be examined from different vantage points (1,), but the most relevant approach is, no doubt, study of dilute solutions themselves. At present, high resolution NMR spectroscopy is the primary tool for determination of three-dimensional structure of oligosaccharides in solution. Optical rotation is also very sensitive to conformation (2) and there is a new, semi-enqpirical theory of optical rotation of oligosaccharides ( ). 

Different schemes and recent results for high-resolution rotational coherence spectroscopy with picosecond and femtosecond laser pulses... 

Over the last years we have explored several advanced techniques for high-resolution rotational coherence spectroscopy (RCS [1]) in order to study the structures of molecules and clusters in the gas phase [2]. We have provided spectroscopic examples demonstrating (i) mass-selectivity (Fig. 1, [3]), (ii) that the rotational constants of the ground and electronic excited states can be obtained independently with high precision (lO MO"5, [4]), (iii) that the transition dipole moment alignment, (iv) centrifugal distortion constants, and (v) information on the polarizability tensor can be obtained (Fig.l, [5]). Here we review results pertaining to points (i), (ii), (iv) and (v) [2,3,5],... 

DilTcrcm schemes and recent results for high-resolution rotational coherence spectroscopy with picosecond and femtosecond laser pulses C. Kiehn, V.-V Matylitsky. A. Weiehert, M.-F. Gclin. W. Jar/eba and B Brutschy 73... 

K. C. Moller and B. P. Stoicheff, Can. ]. Phys., 32, 635 (1954). High Resolution Raman Spectroscopy of Gases. IV. Rotational Raman Spectrum of Cyanogen. 

Much of the beauty of high-resolution molecular spectroscopy arises from the patterns formed by the fine and hyperfine structure associated with a given transition. All of this structure involves angular momentum in some sense or other and its interpretation depends heavily on the proper description of such motion. Angular momentum theory is very powerful and general. It applies equally to rotations in spin or vibrational coordinate space as to rotations in ordinary three-dimensional space. 

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