Experimental Methods

Abstract

When the infrared spectra of gaseous heteronuclear molecules are analysed at high resolution, a series of closely spaced components are observed. This type of structure is due to the excitation of rotational motion during a vibrational transition and is referred to as an vibration-rotation spectrum [1]. The absorptions fall into groups called branches and are labelled P, Q and R according to the change in the rotational quantum number associated with the transition. The separation of the lines appearing in a vibration-rotation spectrum may be exploited to determine the bond length of the molecule being examined.

Harmonic scale factors of fundamental transitions for dispersion-corrected quantum chemical methods

“…[1] This spectroscopic technique observes intra-and intermolecular vibrational motions, as their resonant excitation energies lie in the IR region, i.e., approximately from 100 to 10 4 cm −1 (wavelengths from 0.1 mm to 780 nm). [1,2] In addition to simple absorption/emission IR spectroscopy, [3] there are other techniques, such as vibrational circular dichroism (VCD), which is sensitive to molecular chirality, [4,5] vibrational Raman spectroscopy, [6] inelastic neutron scattering (INS), [6][7][8] infrared/ultraviolet (IR-UV) ion dip spectroscopy, [9] infrared multiple photon dissociation (IRMPD) spectroscopy, [10][11][12][13][14] various messenger-tagging methods (such as helium, nitrogen, or hydrogen molecular tag), [15][16][17][18][19][20] that allow measuring spectra of ions, and vibrational sum frequency generation (VSFG) spectroscopy, that allows to probe molecular motions at the phase interfaces. [21,22] All these vibrational spectroscopy methods allow us to inspect the properties of molecules, ions, and molecular aggregates in the gas, liquid, and solid phases and at the interfaces between phases.…”