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1. |
The 13C free induction decay (FID) was acquired following a single 30o pulse to a sample of iodomethane. The spectrum following Fourier transformation (FT) is given on the right. |
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Describe what would happen to the FID and to the spectrum obtained following FT when : |
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i) |
The pulse angle was increased by a factor of 3. |
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ii) |
The pulse angle was increased by a factor of 6. |
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iii) |
The pulse angle was increased by a factor of 12? |
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iv) |
100 FIDs were accumulated and added together before FT. |
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v) |
The sample was dissolved in a viscous solvent before acquisition of the FID. |
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vi) |
The proton spectrum was saturated for several seconds immediately before (but not during) the acquisition of the FID. |
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vii) |
The 13C spectrum was saturated for several seconds immediately before acquisition of the FID. |
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viii) |
The 1H spectrum was irradiated continuously with strong Rf radiation before and during the acquisition of the FID. |
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Answer |
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2. |
The 1H free induction decay (FID) was acquired following a single 90o pulse to a sample of chloroform (CHCl3). The spectrum following Fourier transformation (FT) is given on the right. |
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Describe what would happen to the FID and to the spectrum obtained following FT when : |
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i) |
The pulse angle was increased to 150o. |
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ii) |
A small amount of an Fe(III) salt was dissolved in the solution before acquisition of the FID. |
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iii) |
16 FIDs were accumulated and added together before FT. |
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iv) |
A second FID was acquired using a 270o pulse instead of a 90o pulse and added to the first before FT. |
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v) |
The sample was dissolved in a viscous solvent before acquisition of the FID. |
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vi) |
The FID was accumulated for twice the acquisition time before FT. |
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vii) |
The proton spectrum was saturated for several seconds immediately before (but not during) the acquisition of the FID. |
| What would happen to the spectrum if 16 FIDs were accumulated, each was transformed and the resulting spectra were added together to give the final spectrum ? | |
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Answer |
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