Page 1 Overlapping Orders Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992. d(sin a + sin ß) = m? For Example: 1 st Order = 400 nm 2 nd Order = 200 nm 3 rd Order = 133 nm Any equivalent m? combinations will share ß values. Calculate the free spectral range: ?? f = ?/(m+1) Page 2 Overlapping Orders Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992. d(sin a + sin ß) = m? For Example: 1 st Order = 400 nm 2 nd Order = 200 nm 3 rd Order = 133 nm Any equivalent m? combinations will share ß values. Calculate the free spectral range: ?? f = ?/(m+1) Blaze Angle (?) Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. Intensity is highest when ß matches the angle of specular reflection. Gratings: often characterized by angular dispersion (D a ) ß ? ß a ß ? ß cos sin sin cos + = = = d m d d a D the angular separation corresponding to a wavelength separation 0 th order Page 3 Overlapping Orders Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992. d(sin a + sin ß) = m? For Example: 1 st Order = 400 nm 2 nd Order = 200 nm 3 rd Order = 133 nm Any equivalent m? combinations will share ß values. Calculate the free spectral range: ?? f = ?/(m+1) Blaze Angle (?) Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. Intensity is highest when ß matches the angle of specular reflection. Gratings: often characterized by angular dispersion (D a ) ß ? ß a ß ? ß cos sin sin cos + = = = d m d d a D the angular separation corresponding to a wavelength separation 0 th order Blaze Angle (?) Blazed gratings direct most of the light towards a higher order band. Optimum Intensity: ß = 2? Blaze Wavelength (? b ): ? b = dsin2? Ingle and Crouch, Spectrochemical Analysis Efficiency drops to ~50% at 2/3 ? b and 3/2 ? b . Page 4 Overlapping Orders Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992. d(sin a + sin ß) = m? For Example: 1 st Order = 400 nm 2 nd Order = 200 nm 3 rd Order = 133 nm Any equivalent m? combinations will share ß values. Calculate the free spectral range: ?? f = ?/(m+1) Blaze Angle (?) Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. Intensity is highest when ß matches the angle of specular reflection. Gratings: often characterized by angular dispersion (D a ) ß ? ß a ß ? ß cos sin sin cos + = = = d m d d a D the angular separation corresponding to a wavelength separation 0 th order Blaze Angle (?) Blazed gratings direct most of the light towards a higher order band. Optimum Intensity: ß = 2? Blaze Wavelength (? b ): ? b = dsin2? Ingle and Crouch, Spectrochemical Analysis Efficiency drops to ~50% at 2/3 ? b and 3/2 ? b . Ingle and Crouch, Spectrochemical Analysis Czerny â€“ Turner Monochromator Slits: determine resolution and throughput Monochromators: often characterized by linear dispersion (D l ) â€“ dx/d? R d : Reciprocal D l a l fD D = Page 5 Overlapping Orders Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992. d(sin a + sin ß) = m? For Example: 1 st Order = 400 nm 2 nd Order = 200 nm 3 rd Order = 133 nm Any equivalent m? combinations will share ß values. Calculate the free spectral range: ?? f = ?/(m+1) Blaze Angle (?) Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. Intensity is highest when ß matches the angle of specular reflection. Gratings: often characterized by angular dispersion (D a ) ß ? ß a ß ? ß cos sin sin cos + = = = d m d d a D the angular separation corresponding to a wavelength separation 0 th order Blaze Angle (?) Blazed gratings direct most of the light towards a higher order band. Optimum Intensity: ß = 2? Blaze Wavelength (? b ): ? b = dsin2? Ingle and Crouch, Spectrochemical Analysis Efficiency drops to ~50% at 2/3 ? b and 3/2 ? b . Ingle and Crouch, Spectrochemical Analysis Czerny â€“ Turner Monochromator Slits: determine resolution and throughput Monochromators: often characterized by linear dispersion (D l ) â€“ dx/d? R d : Reciprocal D l a l fD D = Can change angle of grating to focus different ? on the exit slit. Take-off angle (F) is constant. Change ? to direct different ? towards F ? ?= a + F F = ß - ? m ? = 2 d sin? cosF Ingle and Crouch, Spectrochemical AnalysisRead More

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