能量( Energy)与频率 (frequency) 之间的关系 △E=E2-E1= hy- hO 频率越高,获得的能量越大。 波长越短,获得的能量越大 只有光子的能量恰好等于两个能级之间的能量差时 (即△E)才能被吸收,通过仪器记录,得分子吸收光谱图
能量（Energy)与频率(frequency) 之间的关系 E = E2 - E1 = λ hC hv = 频率越高，获得的能量越大。 波长越短，获得的能量越大。 只有光子的能量恰好等于两个能级之间的能量差时 （即 E ）才能被吸收，通过仪器记录，得分子吸收光谱图
The different regions of the electromagnetic spectrum are shown in Fig. 14.2 Fig 14.2 The electromagnetic spectrum Increasing y Cosmic X-rays (UV Vacuum Near Ⅴ isible(IR) aR and Microwave Ultraviolet Ultraviolet near infrared radio y-rays infrared 0.1nm 200nm 400 nm 800 nm 2 Hr 50 um Increasing
The different regions of the electromagnetic spectrum are shown in Fig.14.2. λ Fig. 14.2 The electromagnetic spectrum Cosmic and γ - rays X- rays (UV) Vacuum Ultraviolet (UV) Near Ultraviolet Visible (IR) infrared (IR) near infrared Microwave radio 0.1 nm 200 nm 400 nm 800 nm 2 μm 50 μm Increasing v Increasing
14.2 Visible and Ultraviolet Spectroscopy 1. What is it ultraviolet spectroscopy ncreasing v Cosmic Vacuum (UV Visible and Near Ultraviolet Ultraviolet y-rays 0.1nm100mm nm 400nm800nm 空气O2,CO2能吸收 紫外光谱可测定有机物共轭体系结构 需在真空条件下测定
14.2 Visible and Ultraviolet Spectroscopy 1. What is it ultraviolet spectroscopy? Cosmic and γ - rays X- rays (UV) Vacuum Ultraviolet (UV) Near Ultraviolet Visible 0.1 nm 200 nm 400 nm 800 nm Increasing v 100 nm 空 气 O2 , CO2 能 吸 收 ， 需 在 真 空 条 件 下 测 定 紫 外 光 谱 可 测 定 有 机 物 共 轭 体 系 结 构
A typical UV absorption spectrum, that of 2, 5-dimethyl 2, 4-hexadiene, is shown in Fig 14.3
A typical UV absorption spectrum, that of 2,5-dimethyl- 2,4-hexadiene, is shown in Fig. 14.3. 200 210 220 230 240 250 260 270 nm Absorbance 吸 光 度 Wavelength 波 长 (nm) Max 242 nm (CH3 ) 2C=CHCH=C(CH3 ) 2 0.1 0.2 0.3 400 nm
In addition to reporting the wavelength of maximum absorption (max ), chemists often report another quantity that indicates the strength of the absorption, called the molar absorptivity, E
In addition to reporting the wavelength of maximum absorption (λmax ), chemists often report another quantity that indicates the strength of the absorption, called the molar absorptivity, ε Lambert-Beer Rule; A = ε C L = - log I Io A----absorbance 吸 光 度 ε --- molar extinction coefficient 摩 尔 消 光 系 数 C----molar concentration of sample L-------the length (in centimeter) 液 层 厚 度