Question

Rotational spectroscopy observe what type of molecule? What is his energy range? Measured molecule properties.

vibrational spectroscopy observe what type of molecule? What is his energy range? Measured molecule properties.

Answer 1

1. Roatational spectra ( microwave spectra) : This spectra arise due to transitions between the rotational energy levels of a gaseous molecule on the absorption of radiations falling in the microwave region. These spectra are shown by molecuels which posses a permanent dipole moment, example: HCl,CO,H₂O vapour, NO etc.Homonuclear diatomic molecules like H₂,Cl₂ ..etc and linear polyatomic molecules such as CO₂, which do not have a dipolemoment , do not show rotational spectra.freqencies and wavenumbers of rotational transitions of molecules are measured.

spectral range= 1-100 cm^-1

^2. vibrational spectra: These type of spectra arise due to the induced transition between vibrational energy levels of a molecule on the absorption of radiation belonging to the infrared region. Irfrared spectra are shown by molecules when vibrational motion is accompanied by a change in the dipole moment of the molecule. This spectra occur in the spectral range of 500-4000 cm^-1.