FIU CHM 4130 - Key_for Chapter_ 7 (3 pages)

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Key_for Chapter_ 7



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CHAPTER 7 Equation 7 17 can be written w Oeff D 1 For a prism monochromator the linear 7 1 CHAPTER 7 dispersion D decreases continuously with increasing wavelength The reciprocal linear dispersion D 1 thus increases as the wavelength becomes longer Hence if Oeff is to 7 1 Equation 7 17 can be written w eff D 1 For a prism monochromator the linear dispersion D decreases withbeincreasing remain constant w thecontinuously slit width must decreasedwavelength accordingly The Forreciprocal a gratinglinear dispersion D 1 thus increases as the wavelength becomes longer Hence if eff is to remain constant w essentially the slit width must over be decreased accordingly For a range gratingThus w instrument D 1 is constant a considerable wavelength instrument D 1 is essentially constant over a considerable wavelength range Thus w does doesnot notneed needtotobe bevaried variedwith withaagrating gratingmonochromator monochromator 7 2 For qualitative analysis it is important to resolve as many absorption bands as possible 7 2 For qualitative analysis it is important to resolve as many absorption bands as possible for identification purposes This consideration often that means slit widths for identification purposes This consideration often means slitthat widths should be as should be as narrow as possible On the other hand for quantitative methods better signal to noise ratios On andthe hence can bemethods obtained better with wider slit widths narrow as possible otherhigher hand precision for quantitative signal to noise ratios and hence higher precision can be obtained with wider slit widths 7 3 7 3 a Omax 2 90 u 103 T 2 90 u 103 5000 K 0 58 Pm or 580 nm b Omax 2 90 u 103 3000 K 0 967 Pm or 967 nm c Omax 2 90 u 103 1500 K 1 93 Pm 7 4 a Et DT4 5 69 u 10 8 W m 2 K 4 u 5000 K 4 3 56 u 107 W m 2 7 6 Spontaneous 8emission occurs when a4 species loses all or part of its excess energy 2 4 6 2 b E 5 69 u 10 W m K u 3000 K 4 61 u 10 W m t in the form of fluorescence or phosphorescence radiation Because the process is random and can occur in any direction the radiation is incoherent Stimulated emission is brought 5 5 69 u 10 8ofWexcited m 2 K 4species u 1500 K 4externally 2 88 u 10 W m 2photons that have c Eby t interaction about with produced energies exactly matching the energy of a transition The photons produced are in phase the 2 90 emission coherent radiation is the 7 5 with a those Omax stimulating 2 90 u 103 T u 103and 2870 1 01 Pm or 1010 nmresult Omax 2 90 u 103 3500 0 829 Pm or 829 nm 7 7 A four level laser system has the advantage that population inversion is achieved 6 4 necessary more system it is only b easily Et than 5 69with u 10a 8three level W m 2 K 4system u 2870InK a4four level 3 86 u 10 W m 2 u 10 m2 cm2 to maintain a number of excited species that exceeds the number in an intermediate energy level that is higher in2 energy 2than the ground state If the lifetime of the intermediate state 3 86 u 10 W cm is brief a relatively few excited species is required for population inversion 1 7 8 The effective bandwidth of a filter is the width in wavelength units of the band transmitted by the filter when measured at one half the peak height Principles of Instrumental Analysis 6ththed Chapter 7 Principles of Instrumental Analysis 6 th ed Chapter 7 Principles of Instrumental Analysis 6 ed Chapter 7 7 10 7 10 From Equation 7 5 d On 2n If first order interference is used one end of the wedge 7 10 From Equation 7 5 d On 2n If first order interference is used one end of the wedge 7 10 From Equation 7 5 d On 2n If first order interference is used one end of the wedge would have a thinckness d of would have a thinckness d of would have a thinckness d of d 700 nm u 1 2 u 1 32 265 nm or 0 265 Pm d 700 nm u 1 2 u 1 32 265 nm or 0 265 Pm d 700 nm u 1 2 u 1 32 265 nm or 0 265 Pm This thickness would also transmit second order radiation of 700 2 350 nm which This thickness would also transmit second order radiation of 700 2 350 nm which This thickness would also transmit second order radiation of 700 2 350 nm which would be absorbed by the glass plates supporting the wedge would be absorbed by the glass plates supporting the wedge would be absorbed by the glass plates supporting the wedge The other end of the wedge should have a thickness of The other end of the wedge should have a thickness of The other end of the wedge should have a thickness of d 400 u 1 2 u 1 32 1 52 nm or 0 152 Pm d 400 u 1 2 u 1 32 1 52 nm or 0 152 Pm d 400 u 1 2 u 1 32 1 52 nm or 0 152 Pm Thus a layer should be deposited with is 0 265 Pm on one end and which tapers linearly Thus a layer should be deposited with is 0 265 Pm on one end and which tapers linearly Thus a layer should be deposited with is 0 265 Pm on one end and which tapers linearly over 10 0 cm to 0 152 Pm at the other end over 10 0 cm to 0 152 Pm at the other end over 10 0 cm toof0 152 at the other end is considerably greater than that for fused 7 11 The dispersion glass Pm for visible radiation 7 11 The dispersion of glass for visible radiation is considerably greater than that for fused 7 11 silica The dispersion of glass for6 9 visible radiation is considerably greater than that for fused or quartz see Figure 7 12 silica or quartz see Figure 6 9 silica quartz see i sin r Figure 6 9 Equation 7 6 7 12 nO dor sin Equation 7 6 7 12 nO d sin i sin r d sin i sin r Equation 7 12 dnO nO sin i sin r 1 u 400 nm sin 45 7 6 sin 5 400 nm 0 707 0 087 503 7 nm d nO sin i sin r 1 u 400 nm sin 45 sin 5 400 nm 0 707 0 087 503 7 nm d nO sin i 1 sin nm sin 45 sin 5 400 nm 0 707 0 087 503 7 nm liner 1 u 400 nm lines mm u 106 nm 1985 1 line lines mm 503 7 nm u 106 mm 1985 1 linenm nm 503 7 mm lines mm u 106 1985 7 13 For first order503 …


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