The NH2 scissors band of methylamine

For the first time the ν4 NH2 scissors band has been assigned in a high-resolution infrared spectrum. A rotationally resolved spectrum of methylamine was recorded using two infrared spectroscopic techniques. A White-type multi-pass cell device coupled to the Bruker IFS 125 HR Fourier transform spectrometer was implemented on the AILES beamline at the SOLEIL synchrotron facility and a room-temperature spectrum of the whole band in the region of 1540–1710 cm−1 was recorded with a resolution of 0.001 cm−1. Then, a low-temperature high-resolution spectrum in the 1622.5–1655.6 cm−1 range of Q and R branches of the ν4 band was recorded using a quantum cascade laser spectrometer. Preliminary assignment was carried out in the NH2 scissors band region, and about 2200 transitions for K from 0 to 6 have been assigned for A, B, and E1 symmetry species. The simultaneous fit of assigned lines using a group-theoretical effective Hamiltonian was not successful; instead simple polynomial series expansions were used for each symmetry and K value.

Construct the Character Table of D7h Point Group and Apply it for Classify the (3N-6) Modes of Vibration for the [7] Cyclacene (Linear) Monoring Molecule

The character table or the table of eigen values for the D7h point group, which is not found in the literature was constructed. The constructed table is used to classify all modes of the vibrational frequencies of the IR and Raman spectra for any compound or molecule that has the D7h symmetry in the Point Group. For that, it was used for classifying all the modes of vibrational frequencies of the [7] cyclacene (linear) monitoring molecule, possessing D7h symmetry. The constructed table was used to classify the symmetry species for the total degrees of freedom, total degrees of transition, total degrees of rotation and for the total degrees of modes of vibration (3N-6) for this tube. The character table was also used to determine the active and inactive modes of vibration in the IR and Raman spectra.Also,determining the polarized and non-polarized vibrational frequencies in the Raman spectrum, and used for describing the complete physical structure of the studied molecule after extracting its geometric shape. The methods of quantum mechanics calculations PM3 and DFT were used for this purpose applying the Gaussian 09 program.

VIBRATE!A program to compute irreducible representations for atomic vibrations in crystals

VIBRATE!is a computer program that uses group theory to carry out factor group analysis of a crystal structure. The symmetry species of the normal modes of vibration are derived, together with information relating to the symmetry-adapted vectors. The program is simple to use, relying on input mainly from a crystallographic information file. The output is presented in a form that should be familiar not only to crystallographers but also to others such as chemical spectroscopists.

Conformational symmetry and vibrational dynamics of polymers

Polymers are an important class of materials, and their conformation dictates their dynamical, thermodynamical, and hydrodynamical behavior. Several spectroscopic and other techniques have been employed to characterize their conformation. However, little use has been made of group-theoretical techniques except in the classification of symmetry species. In the present review, an attempt has been made to correlate normal modes and their dispersion profiles with the conformation of the polymeric systems. This has been attempted in the case of 2-, 3-, 4-fold and α-helical polymers.

Complex symmetrized calculations on ammonia vibrational levels

This paper introduces a fully symmetrized Hamiltonian formalism designed for description of vibrational motion in ammonia (and any XH3 molecule). A major feature of our approach is the introduction of complex basis vibrational wavefunctions in product form, satisfying the complex symmetry species (CSS) of the molecular symmetric top point group (D 3h). The described formalism for ammonia is an adaptation of the approach, previously developed and applied to benzene, based on the CSS of the point group D 6h. The molecular potential energy surface (PES) is presented in the form of a Taylor series expansion around the planar equilibrium state. Using the described formalism, calculations have been carried out on the vibrational overtone and combination levels in 14NH3 up to vibrational excitation energies corresponding to the fourth N-H stretch overtone. The results from the calculations are adjusted to experimentally measured data, in order to determine the values of the harmonic and some anharmonic force constants of the molecular PES.