An implementation of simulated annealing optimization based on 13 Method for enhancing polarization uniformity of c-core
Patent Information
- Application Number
- CN202310542114.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-11
- Publication Date
- 2026-09-22
- Estimated Expiration
- 2043-05-11
AI Technical Summary
这使得不灵敏核的重聚极化转移增强技术只适用于定性的13C核磁共振检测，不能推广到定量检测中
[0030](1)采用模拟退火优化得到的极化转移时间、重聚时间参数集，通过循环叠加，实现了不同13C核的极化均一增强，信号增强倍数的相对标准偏差小于2.5％。
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Figure CN116804724B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of liquid nuclear magnetic resonance detection technology, and particularly relates to a method based on simulated annealing optimization. 13 The method of enhancing the uniformity of C-nucleus polarization is suitable for the detection of samples in the fields of petrochemicals and polymers. Background Technology
[0002] 13 C12 NMR spectroscopy has the advantages of high resolution, wide chemical shift distribution, and low signal overlap, and is widely used in the analysis and characterization of petroleum, polymers, pharmaceuticals, and natural products. It is typically obtained using single-pulse excitation and inverse-gated decoupling. 13 C NMR spectrum. However, due to 13 The natural abundance of C-nuclei is only 1.1%, resulting in low detection sensitivity and requiring a sufficient number of samplings to obtain a signal-to-noise ratio image. 13 C NMR spectrum. Additionally... 13 The C-core has a longer lateral relaxation time, which makes it easier to obtain quantitative data. 13 C12 NMR spectroscopy becomes difficult. Conventional single-pulse excitation and anti-gated decoupling methods are time-consuming and inefficient, limiting their application. 13 Applications of C-NMR in quantitative measurements. To enhance... 13 To improve the intensity of C-NMR signals and reduce testing time, polarization transfer techniques based on J-coupling have been introduced. 13 In C NMR detection. This method will shift the polarization from high gyromagnetic ratio. 1 H nuclei transmit low gyrometric magnetic ratios 13 C core, to improve 13 The polarization of the C nucleus. 13 The polarization of the C nucleus is enhanced, and its NMR signal is also enhanced accordingly, with a maximum enhancement factor of approximately 4. Refocused insensitive nuclei enhanced by polarization transfer (R-INEPT) is one of the classic methods in this field. Integrator analysis indicates that, using the R-INEPT method, the C nucleus in CH, CH2, and CH3 groups... 13 The polarization enhancement factor η obtained by the C nucleus and the J coupling constant of carbon and hydrogen (J) CH ), polarization transition time (Δ T ) and polarization re-aggregation time (Δ R They are related, but their evolution curves are different. For example, when the polarization transition time Δ T =1 / (2J) CH For CH groups, the optimal polarization repolymerization time Δ R =1 / (2J) CHThe enhancement factor is 4, while the signal strength of CH2 and CH3 is zero; when Δ R =1 / (4J) CH At this point, the enhancement factors obtained by CH, CH2, and CH3 are 2.83, 4, and 4.24, respectively. Therefore, in the repolymerization polarization transfer enhancement of insensitive nuclei, the enhancement factors of different groups are... 13 The polarization enhancement obtained by the C nucleus is non-uniform. Even for the same type of group, the polarization enhancement varies due to the different J coupling constants of carbon and hydrogen. 13 The polarization enhancement obtained by the C nucleus is also inconsistent. This makes the re-aggregation polarization transfer enhancement technique for insensitive nuclei only applicable to qualitative applications. 13 C-NMR detection cannot be extended to quantitative detection. Summary of the Invention
[0003] To address the shortcomings of existing technologies, the purpose of this invention is to provide an optimized implementation based on simulated annealing. 13 A method for uniformly enhancing C-nuclear polarization. This method achieves [the desired effect] for primary, secondary, and tertiary carbons in organic compounds within a certain range of J-coupling constants. 13 The consistent increase in C-nucleus polarization resulted in a uniform signal enhancement, shortening the detection time. The sequence is simple, easy to operate, and has strong universality, making it suitable for quantifying organic samples. 13 C-NMR detection provides a new and effective approach.
[0004] To achieve the above objectives, the present invention employs the following technical measures:
[0005] An optimization implementation based on simulated annealing 13 The method for enhancing C-core polarization uniformity includes two stages: simulated annealing optimization and experimental sampling. The simulated annealing optimization includes the following steps:
[0006] Step 1.1: Establish the CH group 1 H- 13 The polarization transfer function P between C CH CH2 group 1 H- 13 polarization transfer function between C and the CH3 group 1 H- 13 polarization transfer function between C
[0007]
[0008]
[0009]
[0010] Where ΔTi Δ Ri Let i and n represent the polarization transition time and polarization reunification time, respectively. A pair of polarization transition times and polarization reunification times constitutes a set of polarization time parameters, where i represents the ordinal number of the polarization time parameter set, n represents the total number of polarization time parameter sets, and J represents the polarization time parameter set. CH Represents the J coupling constant of carbon and hydrogen;
[0011] Step 1.2: Construct the objective function.
[0012]
[0013] y is the objective function.
[0014] Representing the CH groups respectively 1 H- 13 The polarization transfer function P between C CH The maximum and minimum values,
[0015] They represent the CH2 groups respectively 1 H- 13 Polarization transfer function between C The maximum and minimum values,
[0016] They represent the CH3 groups respectively 1 H- 13 Polarization transfer function between C The maximum and minimum values;
[0017] Step 1.3: Use simulated annealing optimization to search for the optimal polarization transition time and optimal polarization refocusing time that minimize the value of the objective function u. The optimal polarization transition time is... The preferred polarization re-aggregation time is
[0018] The experimental sampling phase, as described above, includes the following steps:
[0019] Step 2.1: Load the pre-programmed pulse sequence into the nuclear magnetic resonance spectrometer;
[0020] Step 2.2: Load the set of preferred polarization transfer time and preferred polarization refocusing time parameters obtained in Step 1.3 into a pre-written pulse sequence to obtain a preset optimized pulse sequence;
[0021] Step 2.3: Set the pulse sequence 1 The power and corresponding pulse width of the 90° and 180° pulses of the H nucleus;
[0022] Step 2.4: Set the pulse sequence 1Decoupling method and power of H core;
[0023] Step 2.5: Set the pulse sequence 13 The power and corresponding pulse width of the 90° and 180° pulses of the C core;
[0024] Step 2.6: Set the center frequency, spectral width, gain, number of sampling points, relaxation delay time, number of empty scans, and number of sampling accumulations, where the number of sampling accumulations is an integer multiple of n;
[0025] Step 2.7: Based on the preset optimized pulse sequence obtained in Step 2.2, run the pulse sequence cyclically, perform sampling and accumulation of the sampled signals, and read the optimized polarization transition time sequentially in n steps during each round of sampling and accumulation. and preferred polarization re-aggregation time Parameter set data;
[0026] Step 2.8: Perform Fourier transform and phase adjustment on the accumulated sampled signal to obtain a one-dimensional nuclear magnetic resonance image with enhanced polarization uniformity. 13 C spectrum.
[0027] As described in step 2.1 above, the pre-written pulse sequence is first applied to... 1 A 90° pulse is applied to the H channel, passing through... After a period of time, 1 H channel and 13 A 180° pulse is applied simultaneously to channel C, and then... time, 1 H channel and 13 A 90° pulse is applied simultaneously to channel C, and then... After a period of time, 1 H channel and 13 A 180° pulse is applied simultaneously to channel C, followed by... After a period of time, 1 H channels eliminate J coupling between carbon and hydrogen, while... 13 Channel C acquires the free-induction attenuation FID signal.
[0028] The above describes an optimization implementation based on simulated annealing. 13 The method for enhancing C-nuclear polarization uniformity, during the sampling period in step 2.7, the 1 The H channel uses combined pulse decoupling to eliminate J coupling between hydrocarbons.
[0029] Compared with the prior art, the present invention has the following advantages:
[0030] (1) Using the polarization transfer time and refocusing time parameter sets obtained by simulated annealing optimization, different polarization transfer time and refocusing time parameters were achieved through cyclic superposition. 13The polarization uniformity of the C core is enhanced, and the relative standard deviation of the signal enhancement factor is less than 2.5%.
[0031] (2) The set of polarization transfer time and repolymerization time parameters obtained by simulated annealing optimization is applicable to most organic compounds and has universality.
[0032] (3) The method proposed in this invention can be applied to 13 In quantitative testing of C NMR, the experimental time is significantly reduced.
[0033] (4) The pulse sequence is simple, with few loop steps, and is easy to execute. Attached Figure Description
[0034] Figure 1 An optimization implementation based on simulated annealing 13 Schematic diagram of a pulse sequence that enhances uniform polarization of the C nucleus;
[0035] Figure 2 Here is the chemical structural formula of isooctyl acrylate, where the carbon atoms are numbered from largest to smallest according to their chemical shifts;
[0036] Figure 3 One-dimensional nuclear magnetic resonance of isooctyl acrylate solution 13 C spectrum (where a is the spectrum achieved using a simulated annealing-based optimization method) 13 (b) is a pulse acquisition sequence with enhanced uniformity of C-nucleus polarization; (b) is a pulse acquisition sequence using 45° pulse excitation and anti-gated decoupling. Detailed Implementation
[0037] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0038] Example 1:
[0039] The method proposed in this invention is used to collect isooctyl acrylate solution. 13 C10 NMR spectroscopy is used as an example. 100.0 μl of isooctyl acrylate solution was pipetted into a 5 mm NMR tube, and then 600.0 μl of deuterated chloroform was added to complete the sample preparation. The 5 mm NMR tube containing the sample was placed into the probe of a Bruker 500 MHz NMR spectrometer, and field locking, tuning, and shimming were performed sequentially to complete the pre-test preparation. The following steps are performed according to the operating procedure proposed in this invention.
[0040] An optimization implementation based on simulated annealing 13The method for enhancing C-core polarization uniformity can be divided into two stages: simulated annealing optimization and experimental sampling. Specifically:
[0041] Phase 1: Simulated Annealing Optimization
[0042] Step 1.1: Establish the CH group 1 H- 13 The polarization transfer function P between C CH CH2 group 1 H- 13 polarization transfer function between C and the CH3 group 1 H- 13 polarization transfer function between C
[0043]
[0044]
[0045]
[0046] Where Δ Ti Δ Ri Let J represent the polarization transition time and polarization reunification time parameters, respectively. A pair of polarization transition times and polarization reunification times constitutes a set of polarization time parameters. Multiple sets of polarization time parameter groups constitute a set of polarization time parameters. The subscript i represents the ordinal number of the polarization time parameter group (i = 1, 2, ..., n), and n represents the total number of polarization time parameter groups in the set. CH denoted by J, representing the carbon-hydrogen coupling constant. Simulated annealing calculations revealed that if the total number of polarization time parameter sets, n, is too small, the optimization cannot converge; if the number of polarization time parameter sets, n, is too large, the calculation is time-consuming, and there is no significant performance improvement. In this embodiment, n is set to 8 as the optimal solution.
[0047] Step 1.2: Construct the objective function.
[0048]
[0049] y represents the objective function.
[0050] Representing the CH groups respectively 1 H- 13 The polarization transfer function P between C CH The maximum and minimum values,
[0051] They represent the CH2 groups respectively 1 H- 13 Polarization transfer function between C The maximum and minimum values,
[0052] They represent the CH3 groups respectively 1 H- 13 Polarization transfer function between C The maximum and minimum values.
[0053] Step 1.3: Execute the simulated annealing optimization program written in MATLAB to search for the set of polarization transfer time and polarization re-aggregation time parameters that minimize the value of the objective function y, i.e., the parameter set of the preferred polarization transfer time and preferred polarization re-aggregation time. In this embodiment, when the carbon-hydrogen J coupling constant is between 115 and 195 Hz, the optimized parameter set of the preferred polarization transfer time and preferred polarization re-aggregation time is as follows:
[0054]
[0055] in, Indicates the preferred polarization transition time. The preferred polarization re-aggregation time is indicated by the subscripts 1 to 8 in the parameter set of the preferred polarization transfer time and preferred polarization re-aggregation time, which represent the ordinal numbers (i = 1, 2, ..., 8) of the 8 sets of preferred polarization transfer time and preferred polarization re-aggregation time parameter sets, corresponding to the ordinal numbers of the polarization time parameter sets in step 1.1.
[0056] The parameter set of preferred polarization transfer time and preferred polarization repolymerization time obtained through simulated annealing optimization is universal and applicable to most organic compounds. 13 The method was directly called upon in the experiment to enhance the uniformity of C-nucleus polarization.
[0057] Phase 2, Experimental Sampling
[0058] Step 2.1: Load the pre-programmed pulse sequence onto the Bruker 500MHz nuclear magnetic resonance spectrometer ( Figure 1 (As shown).
[0059] Figure 1 The pulse sequence shown first applies to 1 A 90° pulse is applied to the H channel, after the 90° pulse is applied... 1 The H nucleus produces transverse coherence. After... After a period of time, 1 H channel and 13 A 180° pulse is applied simultaneously to channel C. Then... time, 1 H channel and 13 A 90° pulse is applied simultaneously to channel C, where 1 The 90° pulse of the H channel is completed. 1 Selective population inversion of the H nucleus in the same coupling system 13The population of the C core also underwent selective inversion. 13 90° pulse establishment in channel C 13 The C-core exhibits antiphase single-quantum coherence. Then, it passes through a re-aggregation unit; the specific process is as follows: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] After a period of time, 1 H channel and 13 A 180° pulse is applied simultaneously to channel C, followed by... Time makes 13 The anti-phase coherence of the C nucleus transforms into in-phase coherence. Then, during the sampling period, 1 The H channel employs combined pulse decoupling to eliminate J-coupling between hydrocarbons. Simultaneously, 13 Channel C acquires the Free Induction Attenuation (FID) signal.
[0060] Step 2.2: On a Bruker 500MHz NMR spectrometer, load the optimized polarization transfer time and optimized polarization refocusing time parameter set obtained in Step 1.3 into a pre-programmed pulse sequence to obtain the preset optimized pulse sequence. During the sampling and accumulation process in subsequent Step 2.7, the optimized polarization transfer time is read sequentially in n-step cycles. and preferred polarization re-aggregation time The data in the parameter set is processed in an 8-step loop in this embodiment, as follows:
[0061] Before the first sampling, read the first set of preferred polarization transition times. Preferred polarization re-cohesion time The durations are (2.0886ms, 2.7618ms) respectively.
[0062] Before the second sampling, read the second set of preferred polarization transition times. Preferred polarization re-cohesion time The durations are (1.8966ms, 1.4694ms)² respectively.
[0063] Before the third sampling, the optimal polarization transition time of the third group was read. Preferred polarization re-cohesion time The durations are (1.9460ms, 1.4498ms)3 respectively;
[0064] Before the fourth sampling, the fourth set of preferred polarization transition times was read. Preferred polarization re-cohesion time The durations are (2.3666ms, 1.1763ms)4 respectively;
[0065] Before the 5th sampling, read the 5th set of preferred polarization transition times. Preferred polarization re-cohesion time The durations are (4.8269ms, 3.6760ms) respectively.
[0066] Before the 6th sampling, the 6th set of preferred polarization transition times was read. Preferred polarization re-cohesion time The durations are (8.8172ms, 4.2108ms) respectively.
[0067] Before the 7th sampling, the 7th set of preferred polarization transfer times was read. Preferred polarization re-cohesion time The durations are (4.2419ms, 3.6579ms) 7 respectively;
[0068] Before the 8th sampling, read the 8th set of preferred polarization transfer times. Preferred polarization re-cohesion time The durations are (2.0577ms, 1.0821ms) 8 respectively;
[0069] Before the 9th sampling, read the first set of preferred polarization transfer times again. Preferred polarization re-cohesion time The durations are (2.0886ms, 2.7618ms) respectively.
[0070] Subsequent sampling follows the same pattern, with the sampling cycle repeated. The number of samples is an integer multiple of n. In this embodiment, sampling ends when 64 samples have been taken.
[0071] Step 2.3, Pulse Sequence 1 The power of the 90° and 180° pulses of the H nucleus was set to -12.58dB, and the corresponding pulse widths were set to 11.4μs and 22.8μs, respectively.
[0072] Step 2.4, Pulse Sequence 1 The decoupling method for the H core is set to Waltz16 combined pulse decoupling with a power of 6.28 dB.
[0073] Step 2.5, Pulse Sequence 13 The power of the 90° and 180° pulses of the C core is set to -18.23dB, and the corresponding pulse widths are set to 10.8μs and 21.6μs, respectively.
[0074] Step 2.6: Set other parameters: center frequency O1P = 78.0ppm, spectral width SW = 160.3ppm, gain RG = 203, number of sampling points TD = 32,768, relaxation delay time D1 = 2.0s, number of empty scans DS = 4, number of sampling accumulations NS = 64. The number of sampling accumulations NS should be set to an integer multiple of n, and the accumulation starts from 0.
[0075] Step 2.7: After completing the parameter settings, run the pulse sequence in a loop and perform sampling and accumulation of the sampled signals.
[0076] The pulse sequence is cyclically read into the optimized polarization transition time and polarization refocusing time parameter set. During each round of cyclic sampling and accumulation, the optimized polarization transition time is read sequentially in n steps. and preferred polarization re-aggregation time Parameter set data, each time a set of preferred polarization transfer times is read in and preferred polarization re-aggregation time parameters The polarization is transferred and refocused according to the preset optimized pulse sequence, and then a sampling and accumulation are performed until the NS (i.e., 64 in this embodiment) cycles are completed to end step 2.7.
[0077] Step 2.8: After the cumulative sampling is completed, perform Fourier transform and phase adjustment on the accumulated free induction decay signal (FID) to obtain a one-dimensional nuclear magnetic resonance with enhanced polarization uniformity. 13 C spectrum (with appendix) Figure 3 (as shown in a).
[0078] In the aforementioned technical measures, the key to this invention is the parameter set of preferred polarization transfer time and preferred polarization repolymerization time obtained through simulated annealing optimization, corresponding to step 1.3. This parameter set contains 8 sets of preferred polarization transfer time and preferred polarization repolymerization time parameters, applicable to most organic compounds and possessing universality. Running the pulse sequence developed in this invention, the preferred polarization transfer time and preferred polarization repolymerization time parameters obtained in the key step 1.3 are read sequentially in 8-step cycles. Through cyclic superposition, the problem of repolymerization polarization transfer being modulated by different functional groups and different C-H J coupling constants is solved. 13 The problem of non-uniform enhancement of C-nucleus polarization. This non-uniform enhancement limits re-cohesion polarization transfer techniques to qualitative applications. 13 C-NMR detection cannot be applied to quantitative detection. By combining key step 1.3 with other steps of this invention, the influence of C-H J coupling constant modulation is effectively eliminated, achieving... 13 The consistent increase in C-nucleus polarization resulted in a uniform signal enhancement, shortened detection time, and facilitated the quantification of organic samples. 13 This invention provides a new and effective approach for C-NMR detection. The optimal polarization transfer time and optimal polarization refocusing time parameter set obtained through simulated annealing optimization are not used in existing polarization transfer enhancement techniques, representing a novel technical approach.
[0079] The isooctyl acrylate used in this embodiment is a chemical raw material with the chemical formula C. 11 H 20 O2 contains 2 primary carbons (CH3), 6 secondary carbons (CH2), 2 tertiary carbons (CH), and 1 quaternary carbon. Its structural formula is shown in the attached figure. Figure 2As shown, the carbon atoms on the framework are numbered from largest to smallest chemical shift. This invention employs a simulated annealing optimization method. 13 A method for enhancing C-nuclear polarization uniformity was used to collect isooctyl acrylate solutions. 13 C spectrum (with appendix) Figure 3 a) 64 samples were collected over an experimental time of 193 seconds. For comparison, a 45° pulse excitation and inverse gating decoupling sequence was used to acquire quantitative data for this sample. 13 C-spectrum, 64 samples, experimental time 715 seconds (see attached) Figure 3 b). The collected data 13 The C-spectrum was integrated, and the results are listed in Table 1. The data collected by the method proposed in this invention... 13 In the C-spectrum, the integrated areas of each resonance peak are basically equivalent, with an average integrated area of 0.99. The relative standard deviation is 1.89%, which is close to the quantitative test results (1.42%) of the 45° pulse excitation and anti-gated decoupling sequence. This is consistent with the results obtained from this sequence. 13 Compared to the C-spectrum, the method proposed in this invention collects... 13 In the C spectrum, the average integral area of each resonance peak increased by 2.10 times, achieving... 13 The uniformity of C nucleus polarization was enhanced, while the experimental time was reduced by 73%. The carbon atoms numbered in Table 1 are as follows: Figure 2 As shown.
[0080] Table 1. One-dimensional nuclear magnetic resonance of isooctyl acrylate 13 The integral result of the C spectrum (A, enhanced polarization homogeneity) 13 C-spectral integration area; B, 45° pulse excitation and anti-gating decoupling 13 C-spectral integral area;
[0081]
[0082] It should be noted that the specific embodiments described in this invention are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains can make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.
Claims
1. An optimization implementation based on simulated annealing 13 The method for uniformly enhancing C-nucleus polarization is characterized by... The process includes two stages: simulated annealing optimization and experimental sampling. The simulated annealing optimization includes the following steps: Step 1.1: Establish the CH group 1 H- 13 The polarization transfer function P between C CH CH2 group 1 H- 13 polarization transfer function between C and the CH3 group 1 H- 13 polarization transfer function between C Where Δ Ti Δ Ri Let i and n represent the polarization transition time and polarization reunification time, respectively. A pair of polarization transition times and polarization reunification times constitutes a set of polarization time parameters, where i represents the ordinal number of the polarization time parameter set, n represents the total number of polarization time parameter sets, and J represents the polarization time parameter set. CH Represents the J coupling constant of carbon and hydrogen; Step 1.2: Construct the objective function. Let y be the objective function. Representing the CH groups respectively 1 H- 13 The polarization transfer function P between C CH The maximum and minimum values, They represent the CH2 groups respectively 1 H- 13 Polarization transfer function between C The maximum and minimum values, They represent the CH3 groups respectively 1 H- 13 Polarization transfer function between C The maximum and minimum values; Step 1.3: Use simulated annealing optimization to search for the optimal polarization transition time and optimal polarization refocusing time that minimize the value of the objective function y. The optimal polarization transition time is... The preferred polarization re-aggregation time is 2. The implementation based on simulated annealing optimization as described in claim 1 13 The method for uniformly enhancing C-nucleus polarization is characterized by... Experimental sampling includes the following steps: Step 2.1: Load the pre-programmed pulse sequence into the nuclear magnetic resonance spectrometer; Step 2.2: Load the set of preferred polarization transfer time and preferred polarization refocusing time parameters obtained in Step 1.3 into a pre-written pulse sequence to obtain a preset optimized pulse sequence; Step 2.3: Set the pulse sequence 1 The power and corresponding pulse width of the 90° and 180° pulses of the H nucleus; Step 2.4: Set the pulse sequence 1 H-core decoupling method and power; Step 2.5: Set the pulse sequence 13 The power and corresponding pulse width of the 90° and 180° pulses of the C core; Step 2.6: Set the center frequency, spectral width, gain, number of sampling points, relaxation delay time, number of empty scans, and number of sampling accumulations, where the number of sampling accumulations is an integer multiple of n; Step 2.7: Based on the preset optimized pulse sequence obtained in Step 2.2, run the pulse sequence cyclically, perform sampling and accumulation of the sampled signals, and read the optimized polarization transition time sequentially in n steps during each round of sampling and accumulation. and preferred polarization re-aggregation time Parameter set data; Step 2.8: Perform Fourier transform and phase adjustment on the accumulated sampled signal to obtain a one-dimensional nuclear magnetic resonance image with enhanced polarization uniformity. 13 C spectrum.
3. The implementation based on simulated annealing optimization according to claim 2 13 The method for uniformly enhancing C-nucleus polarization is characterized by... The pre-written pulse sequence in step 2.1 is first processed... 1 A 90° pulse is applied to the H channel, passing through... After a period of time, 1 H channel and 13 A 180° pulse is applied simultaneously to channel C, and then... time, 1 H channel and 13 A 90° pulse is applied simultaneously to channel C, and then... After a period of time, 1 H channel and 13 A 180° pulse is applied simultaneously to channel C, followed by... After a period of time, 1 H channels eliminate J coupling between carbon and hydrogen, while... 13 Channel C acquires the free-sensing attenuation FID signal.
4. The implementation based on simulated annealing optimization according to claim 3 13 The method for uniformly enhancing C-nucleus polarization is characterized by... During the sampling in step 2.7, the 1 The H channel uses combined pulse decoupling to eliminate J coupling between hydrocarbons.