SU644226A1 - Method for observing nuclear magnetic resonance - Google Patents

Abstract

1, METHOD OF MONITORING NUCLEAR-. GO MAGNETIC RESONANCE, which involves exposing the sample under investigation to a constant magnetic field and a high-frequency magnetic field perpendicular to it with an amplitude not less than the average internal magnetic field, and registering the nuclear magnetic component, longitudinal to the constant magnetic field, relative to the constant magnetic field, at the frequency of nuclear magnetic resonance in an effective magnetic field H 3 < pqj in a rotating coordinate system, characterized in that, in order to increase the resolution / periodic velocity By a coarse change in the phase and / or frequency of the high-frequency magnetic field, they provide a periodic change in the direction of the magnetic field H ^ ff by an angle that is a multiple of ± '^ li and the formation of ecr signals in this field, and the specified component, the nuclear magnetization, is recorded in as a continuous sequence of signals caused by axo.J < hp ^^ Gfi4 ^ 4 ^ Yuyu

Description

2. The method according to p. I / from l and, h and uad and with the fact that. after switching on the high-frequency magnetic field, the frequency is kept constant, and after a time h, over a distance of more than a time of spin-spin relaxation, nuclei in the field efsr, change to gamma 2gs51p (Ne (rf / t / gI), where H; is the magnitude of the half-amplitude of the high-frequency magnetic field, and after a time (1211 / .CH: eff-f ,, where the is the magnetic; gyro. magnetic ratio is changed by that value in the opposite direction, and repeat with a period of 2 1}, ./

. 3. Method of / p, about tl and h and ..... so that after switching on / yyё1ekdfremennogo magnetic field F °. remain unchanged, and the frequency through time ti is changed to the shape of Ne1 / (No-s / y), where H r / Zhenosti constant constant fire; | , s - the initial sound frequency of the high-frequency magnetic field, and through time l

 Unff W, g

setting, pour in the original frequency value, and the process indicated is repeated with a period of 2i, +,

4. The method according to p. 1, that is, and with the fact that after turning on the high-frequency magnetic field, its phase is changed by time c to the value of ilf, while at the same time, the research institute has a value of 2y (Ho-so (y),, then after time h С,, where n or 2, the phase is changed by ± and and I set the initial frequency value, and the specified process will be with a period of 2 п1).

- 5. The method according to p. 4, characterized in that the time Ct is set equal to the value of t - 21) / y Yeff, where in is an integer, is not the preceding spin-spin relaxation time of the nuclei in the field Neff

The exclusion is related to the method of observing nuclear magnetism resonance, and it can be used for research in the field of physics of physics; What is the body, hyy1y1icheko physics, bcdtugsh :: and so on. , E.g. izychejHy ctpVktypy substance tsvizheni and vzaimbdeystvi constituting its atoms and moLok hl from West method observation NMR aklyuchakvdiys that on the analyzed o6pai3efx vovdeystvuyugt go nnym magnetic field Id and perpendicular to it the high frequency MaiHjtfHbaM field with frequency, . Close to the frequency of NMR in the field of Nd, it is based on the ratio with «) in y HQ where y is the reliable gyromagnetic ratio. In addition to the TBGB, the sample is affected by an additional constant magnetic field parallel to the Ho field. High-frequency and Additional magnetic fields are included in the form of pulses in a specific program that ensures the formation of an echo signal in an effective magnetic field in a rotating coordinate system. The echo signal is recorded after the high-frequency magnetic field is turned off by measuring transversely and with respect to the field H of the component of the nuclear sample magnetization at the frequency Wo.

To carry out this method, it is necessary to repeat the experiment multiple times with different durations of the impulse of the high-frequency magnetic field and with a large time interval between each of them, which makes it very difficult and unsuitable

; Schyroxego application. Besides,

  This option does not have a sufficiently strong value for the Dipole – dipole interactions, and therefore the resolution of the eio is limited to hundreds of hertz; . .

well known is the method on л lk | Denis; I have NMR, which allows us to obtain NMR spectra in solids; tejtax. Finding of 10 times without the use of complex and expensive pulse equipment,

Etrtsnrsob whistle. $ tom, w; th on the image; They are affected by a constant magnetic field, Nd, and perpendicular to it, a high-frequency magnetic field, which includes a jump hopper up to a value not less than the Heirp value of the internal magnetic field. the field in the matrix, and the component of the nuclear magnetisation of the sample is recorded, which is a longitudinal constant magnetic field at the NMR frequency in an effective magnetic field Nfsr in the rotating coordinate system.

25 Iole is defined by the ratio

and J / u 5 “Eff-Mo Y)

where H (, is the magnitude of the half-amplitude you; cfcrf magnetic

Pol) 03 - frequency of the high-frequency magnetic field. When the high-frequency magnetic field is hopped on. The magnitude of the sample indicated above, HangaB initially along the field o, doesn’t pretreat around the floor with the frequency, SioX Efsr. This is a component of the nuclear magnetization perpendicular to the field H gepqj, and the mountain ridge with the same frequency of 52. This component induces in the receiver to the carcass, located along the id field, a free induction signal at a frequency that is registered by a receiver connected to this coil. This method provides a resolution of the NMR spectra in solids in a series of several hundred hertz. The inventive goal is to increase the resolution of the ability, - The goal is achieved by the fact that a periodic abrupt change in the phase and / or frequency of the high-frequency magnetic field provides a periodic change in the direction of the magnetic field of dsrc by an angle multiple of and the formation of echo signals in this field , and the indicated component of nuclear magnetization is recorded in the form of a continuous sequence of echo signals, which the program ocsm ectv etsc follows. In the case of a phase change after switching on the high-frequency magnetic field, its frequency is kept constant, and the phase time ti, not exceeding the time of SPIN-SPIN relaxation of the nuclei in the Ieff field, is changed by the value of 2pch: 5 pN (pcp / t15 N:, where HI is the height of the half-amplitude of the high-frequency magnetic field, and through BpeMH-tj- / JCHj is changed by the same amount in the opposite direction, and this process is repeated with a period of 1) In the case of a change in the frequency after the high-frequency magnetic field is turned on, are unchanged, and the frequency is the time Cf is changed by Jf (), where the HQ is the intensity of the dc magnetic field, co is the initial frequency of the high-frequency mag, the n-field, and after 15 (1; /) CHm) | in / sets the initial value frequencies, moreover, this process is repeated with a period of 22i-t-2. In the case of a change in phase and frequency after switching on the high-frequency magnetic field, its phase through time (change by the value of tll while simultaneously changing the frequency by the value of 2 U (HO - with /) then after a time P., where or 2, change the phase to iff and set The initial value is in frequency, and this process is repeated with a period of 2n LI. In this case, to achieve the maximum resolution of the NMR spectrum, It is set to the value of m H ff, where m is an integer not exceeding the time-spin spin of nuclei fA) On .fig. Figure 1 shows schematically the magnetic fields acting on a sample in a rotating coordinate system, and the movement of the nuclear magnetization of the sample in the event of a change in the phase of the high-frequency magnetic field; in fig. 2 - the same, in the case of a change in the frequency of the high-frequency magnetic FIELD; in fig. 3 - the same, in the case of a simultaneous change in the phase and frequency of the high magnetic field. . The test sample is placed in a constant 5-polarizing magnetic field (HO vector), around which with frequency (the vector n rotates, the component of the high-frequency magnetic field, rotates in the direction of the Larmor precession of the nuclear magnetization and is equal to the half-amplitude of the high-frequency field. In the system, rotational vector with vector H,, the magnetic field Neff acts on the sample under study, being equal to 0 with arcco5 (Ho-w (Haf-pl in such a coordinate system for the precession of a nuclear magnetized M) occurs around the field Neff with frequencies When a high-frequency magnetic field is jumped on to a value of 2H, exceeding the average value of the internal magnetic field, and in the sample, a component of the nuclear magnetization M, M sine, perpendicular to the field Efsr and rotating around it with the frequency, appears. an inductance coil located along the field, HO, is a free induction signal at a frequency .fl, which is recorded using a receiver connected to this coil. Due to the dipole-dipole interactions of the nuclei with each other and the inhomogeneity of the Hdff field, caused by the inhomogeneity of the H and the Node magnetic fields, the moments in different parts of the sample precess at different speeds and, over time, are precessioned, i.e. are phased out (M. and ALg in FIG. 1). This leads to the magnetization W, and to the decay of the free induction signal, which is equivalent to the NMR line in the Cdpf – t – 1t6-th and NMR line in this field / Essential yyyfffffl and gS - Dy6-flax1Xf iyyyyyyyyyyyyy I exclude a signal. the choice of an angle of 9 equal to the value of HTa} oB Qo Qrccos (l- {f}, where about 9p is the so-called first magic angle. The contribution of the nonhomogeneity of the floor H-efor to the decay rate of the free induction signal in this field is eliminated by periodically looking and, emé (Neni phase and / or frequency is high hour,; trtrn. field according to the program, ensure that the periodic change of the magnetic field is directed by the Chaff at an angle multiple of li / l and forming into this field. In particular, it is necessary to change the phase according to the following program: through time, after switching on the high-frequency magnetic field, Circumferential or complete decoding into tori of nuclear magnetic moments М, 1л7 П: ШГ $ π7 Фа н р измен измен is changed by Cf fJarcsin (Tff SCHKKTТl @ in Cf 12 (f .. ,, г upij ITOM the field Hgmm grows ;, „.. The direction from, with the constant, and it changes by the angle of the original direction: After a time of 7 / G Eff ja which are the nuclear magnetic moments of A / C, LG, they turn by the angle $ around the new direction of the Nesrf field, the high-frequency phase is not; spasmodically, they change the same magnitude of the inverse directions, as a result of creasing yat yor n: Zhzh 1 nde SHY1Y: ylShSh 1Sh |; The effective magnetic moments M (and g2 turn out to be as if rotated by an angle of 1 around this field and transversely; yy; places.S.P) are shown; and the slightest movement of the vectors W and Mj is of the curved lane. In the initial direction of the field HgJrrfpp, their phasing proceeds and at the moment .. lulii 2 they merge into one vector, forming an echo signal, amplitude) of Г6 Ш pressure from the nebdornbdnist field H-: eff. The subsequent changes in the phase with a period of 7 i + f2 will lead to the FFR of the E5 “ZHYYY-hisNy SedSlot ecr in the time interval 2 (2t44 Co), 4 (g, +, v, etc., these signals are recorded in the vice-continuous sequence. , on 4atCTo yo with the help of P1C) Yemennaya coil in TT “tr ,, .. T, T, n ,,. ., ..-, l ductivity, located along a field of HO. To obtain a large number of signal echoes, which is Necessary for., a continuous reproduction of the NMR spectrum, the time does not exceed the time of 7y-1 spy-rd relaxation of the field in the Hdff field, With 5 Using a high frequency phase change. The frequency field can also be measured - the spin-spin efflux of YY f - i L 5li-u. .

644226 derv (), i.e., measuring the time of decay of the nuclei along K) Tb pbl, in the case of changing the phase to a button after a time longer than the single spin relaxation time in the field Tdff, beyond the component tori. the magnetization perpendicularly decays and the longitudinal to be measured is equal to Msoab. To measure the component in consecutive time periods, for example, a mixed program for changing the phase of a CCA frequency field is used. After time 2, its phase is changed by the aforementioned if value, as a result of which the sod is magnetized; The third direction of the field is JT 5mq). Rotated around it, this magnetization | induces an induction signal in the receiving coil, detuning the magnetic moments of the sods and reducing the re: positive vector; turf ;; magnetization. For him, after a time of sd, much less than time 1, the phase of the rysococial-totrcgrl is changed to the same value in the opposite direction, i.e. Such a direction, which is maintained for a time of H / y, by which its specimen magnitude rotates at an angle around Neff, and then again repeats the indicated phase change. As a result, at the moment of time tj-ir 2 + 2, the sample magnetization turns out to be phased and unnatural. “Directed to the floor of the Ydff, which is the initial direction, the signal in the receiving coil recorded the echo signal at the moment of time. For formed and; The echo series described above is periodically repeated in time, and the time I / is determined from the decrease in their amplitude. The formation of the signals of the extr with the change of the frequency of the high frequency of the magnetic field is carried out by the slider) 1 In a manner (see Fig. 2). After time i of the pre-switching on of the indicated field, its frequency is jumped by jfHgmcp / / (HoCJ / y). In this case, the component f. The effective magnetic field along i becomes equal NoUn o) / a its equal to Zeff IeffN, / (| But.-and / y |) / and the field Me (the rue turns rotated by an angle ff / 2. Through time tj / u1 O f for which the magnetic moments and, M2 are rotated by an angle and around the floor of the neft, establish the initial value of the frequency of the high-frequency field. As a result, ds essv & s are the initial direction and magnitude of the effective field, and at the time of time 2, f 2 there is a full phasing, nuclear magnetic moments of MI, N2 with the formation of a signal echo. taxable changes in frequency with a period will lead to the formation of a series of echo signals at times 2iri, 4Ci), 2C, 4tj), etc. . The formation of echo signals using a simultaneous change in the phase and frequency of the high-frequency magnetic field is schematically shown in Fig. 3. After the time it is turned on, the high-frequency magnetic field is changed in phase by the value of t h while the frequency changes by 2y (Hg- Q / y). As a result, the magnitude of the POL.I.Is) ff remains unchanged, and its direction changes by an angle i with respect to the original direction. This leads to a change in the direction of motion of the vector and nuclear magnetization MV and Ug to the opposite, as a result of which they are phased out. At time point 5t the vectors M and M merge into one AND, directed along the field HO, to form an echo signal at the frequency. After a time where (or 2, 6), the high-frequency field is again abruptly changed to i (and the initial

Afe

H,

frequency value, whereby the field takes the initial direction. Subsequent similar changes in phase and frequency with a period of 2riti will lead to the formation of a series. echo signals at time points 2 (2 (,) j J (2t,), 4 (etc. These signals as their continuous sequence are recorded at the frequency SZo with the help of the HHgjyKTBBHocTH receiving coil located along yol Nd. To achieve the maximum resolution of the NMR spectrum when implementing such a program, time i is set to the value of m -21 / Nzff, where I1 is an integer, i.e. a multiple of the rotation period of 41 nuclear magnetization around the Ndod field, and i must not exceed the spin-spin relaxation time der in this field. At the same time, with the exception of the contribution Along with the field at the rate of decay of the amplitude of the echo signals, effective averaging of the so-called nonsecular part of the dipole – dipole interactions of the nuclei also occurs, which does not vanish at EE-9o and explains the further increase in the NMR spectrum resolution in this case ...

Claims (4)

1. NUCLEAR OBSERVATION METHOD. OF MAGNETIC RESONANCE, which consists in exposing the test sample to a constant magnetic field and a high-frequency magnetic field perpendicular to it with an amplitude of at least the average value of the internal magnetic field in the sample and recording the component of nuclear magnetization, longitudinal relative to the constant magnetic field, at the frequency of the nuclear magnetic resonance in an effective magnetic field H e <p <p in a rotating coordinate system, characterized in that, in order to increase the resolution, periodic koobraznym phase change and / or frequency of the RF magnetic fields provide a periodic change in the direction of the magnetic field Nesrf an angle and forming a multiple echo signals in this field, and said com-, ponent nuclear magnetization is recorded as a continuous sequence caused by echo signals. £ J. 644226 2. The method according to π. 1, on behalf of Yushch and I with the fact that. after switching on the .. high-frequency magnetic field, its frequency is kept constant, and the phase after a time h, exceeding the time of spin-spin relaxation _; nuclei in the field Η ₃ φφ, change by led. rank + 2. args5 <n (N _{e <P} f / t / 2 ¹ N _g ), where -: the half-amplitude of the high-frequency “magnetic field, and after a while. ijrii ', where γ is the nuclear gyro. magnetic ratio, change by the same value in the opposite direction. moreover, this process is repeated with a period of 2 ΐ, 2 .. ’ 3. 'The method according to π. 1 of licha- t, u and u nd with I the fact that post-inclusion in the high-frequency magnetic field, '' ^he .F ^al have ostaylyayut unchanged, a 'frequency through if it is converted to've lichinure / (Ηθ-ω / y ), where Н _{о -} Intensity of a constant magnetic field, ω - initial value of hour-. The frequencies of the high-frequency magnetic field, and after time t * = - set the initial value of the frequency, moreover, this process ^is repeated with a period. 4, The method of π. 1, characterized in that after turning on the high-frequency magnetic его field, its phase ’after time b is changed’ by a value of + ί ί while the frequency is changed by a value of 2y (H ₀ -o / y), then after a time h C, where η = 1 or 2, change the phase to fit and set the initial frequency value, and this process is repeated with a period of 2 ni. .5 "Method according to and. 4 of Whitlock and hours and Yu-u and d with me that time £ <is set equal to the value of / at the March ₄ ff, where the W - integer '- not exceeding the spin-spin relaxation time of the nuclei in POLENOV _e ff . -. l '! . 1.-