810. 6 Photochemistry It-class reading Levine, pp. 800-804 photochemistry
§10. 6 Photochemistry Out-class reading: Levine, pp. 800-804 photochemistry
§10.6 Photochemistry 6.1 Brief introduction of light 1)Photochemistry The branch of chemistry which deals with the study of chemical reaction initiated by light 2) Energy of photon The photon is quantized energy: light quantum ho Where h is the Plank constant, C the velocity of light in vacuum, a the wave-length of the light, and v the wave number
6.1 Brief introduction of light The branch of chemistry which deals with the study of chemical reaction initiated by light. 1) Photochemistry The photon is quantized energy: light quantum hC C = h = h = Where h is the Plank constant, C the velocity of light in vacuum, the wave-length of the light, and the wave number. 2) Energy of photon §10. 6 Photochemistry
§10.6 Photochemistry 6.1 Brief introduction of light 3×105m3.98×108kJmo1 radIo s=h 3×101m3.98×104 kJ mol1 micro-wavel 6×104m199×101 k mol1 Microwave Ifar-infrared I chemistry 3×105m3.99 k. mol1 Inear-infrared 800 nm 149.5 kJ mol-1 visible 400 nm 299.0 kj mol-1 photochemistry lultra-violet I 150 nm 797.9 kj mol-1 vacuum violet 50nm239×104 kJ mol1 radiochemistry 5nm1.20×109 kJ mol1 I X-ray
6.1 Brief introduction of light §10. 6 Photochemistry
§10.6 Photochemistry 6.1 Brief introduction of light 1: intensity of light, 4)Interaction between light and media d I adx x: the thickness of the medium a: the absorption coefficient absorption Light transmission I=loxp(ax) beam Lambert’slaw Reflection Scattering refraction I=lo[1-expax)] d Beer’slaw: lo exp(-acx
4) Interaction between light and media exp( ) I = I0 −ax adx I dI − = [1 exp( )] I I0 I I0 ax a = − = − − I: intensity of light, x: the thickness of the medium, a: the absorption coefficient. 6.1 Brief introduction of light Beer’s law: 0 exp( ) a I I cx = − Lambert’s law §10. 6 Photochemistry Light beam
§10.6 Photochemistry 6.2 Physical processes of Excitation and decay (1)Photoexcitation Upon photo irradiation, the molecules or atoms can be excited to a higher vibrational or rotational states Electronic Excitation of x-x A+hy→A Excited state The lifetime of the excited atom is of the Ground state order of 10-8s. Once excited, it decays at nce A absorption F=fluorescence IR spectrum
Upon photo irradiation, the molecules or atoms can be excited to a higher electronic, vibrational, or rotational states. A + h → A* The lifetime of the excited atom is of the order of 10-8 s. Once excited, it decays at once. IR spectrum 6.2 Physical processes of Excitation and decay (1) Photoexcitation: §10. 6 Photochemistry