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Separation of 13C spectra of polyurethane soft and hard segments by ROSY_NM200013E

The ROSY (Relaxation Ordered SpectroscopY) is a method in which the 13C CPMAS spectrum of a mixture is classified by a longitudinal relaxation time of 1H, and the 13C CPMAS spectrum is displayed separately for each substance. In solution NMR, each peak in the 1H spectrum has its own longitudinal relaxation time. In solid-state NMR, however, spin diffusion occurs due to the dipolor interaction between 1H, and all 1H have the same longitudinal relaxation in the domain within a certain distance. The 13C spectrum can be separated for each domain by using this difference in relaxation time of 1H. The longitudinal relaxation time (T1H) obtained by the saturation recovery method as shown in Fig.1a is usually used to separate the 13C spectrum of the mixture. The size of the domain that can be separated by this method is about 100 nm. To separate domains smaller than this, a measurement using the relaxation time at rotational flame (T1ρH) obtained by the spinlock method as shown in Fig.1b is effective. The domain size that can be separated by T1ρH is about several nm, and it is possible to determine the phase separation structure of block copolymers and the molecular compatibility.

The Use of Dispersive Solid Phase Extraction in the Detection of Pesticides in Cannabis Flower by GC-MS/MS

This study presents a comprehensive method for the analysis of gas chromatograph (GC)-amendable pesticides in Cannabis flower. Furthermore, this method uses dispersive solid phase extraction (dSPE) to help mitigate matrix effects that are common in the flower extract. Three selected reaction monitoring (SRM) transitions were used for each target pesticide. This study was focused on developing a robust and sensitive method for GC amendable pesticides in Cannabis flower for use in the state of California. However, LC-MS/MS would also be required to analyze the complete California pesticide list.

Strong interaction between light and electrons (4) "Transmission ESR/FMR measurement method"

Interaction between microwave photon and spins means in other words, interaction between resonating photon in a closing space and spins. Thus, measuring spectra using a non-resonant device can prevent the Purcell effect or strong coupling from distortion of intrinsic spectra. Figure 1(a) is a drawing expressing a typical spectroscopy. A light source irradiates light to a sample, and transmitted light is detected. A simple and non-resonant wave guide, as shown in Fig.1(b), can provide absorption spectra of para- and ferromagnetic samples which have a high spin density.

Strong interaction between light and electrons (2) "Four states of interaction between photon and spins"

A conventional ESR spectrometer uses a cavity for microwave irradiation and detection of ESR absorption. On the resonance state, it can be considered as a model that spins absorb energy of ℎ𝜈=𝑔𝜇𝐵𝐵 and then release it to the lattice system one way, where h: Planck constant, ν: frequency, g: g-value, μB: Bohr magneton, and B: magnetic flux density. However, the interaction between photon of microwave and spins of electrons is a little more complex in fact. Figure 1 is a modelized drawing that expresses energy flow of microwave photon and spins. The cavity resonates with angular frequency 𝜔c, relaxes with velocity of 𝜅𝑐=𝜔𝑐 / 𝑄𝑢 , which is inversely proportional to unloaded Q value of the cavity. On the other hand, spins do precess with an angular frequency of 𝜔𝑚= 𝛾𝑒 𝐵𝑚 under the static magnetic field 𝐵𝑚. When the resonant condition of 𝜔𝑐 = 𝜔𝑚 is satisfied, excited electron spins that absorbed microwave energy relax with the velocity of 𝛾𝑚 (half width: half width at half maximum (HWHM)), which corresponds to spectral line width. At this time, photon and electron spins exchange energy with a coupling constant 𝑔𝑚. The coupling constant 𝑔𝑚 is expressed as[1] 数式 where 𝜂𝑚𝑠𝑞𝑟𝑡 is the square root of the filling factor of the cavity, 𝛾𝑒 is gyromagnetic ratio of the electron, ℏ is reduced Planck constant (h/2π), 𝜇0 is vacuum permeability, 𝑉𝑐 is the volume of the cavity, N is number of magnetic ions, and S is spin quantum number.

Strong interaction between light and electrons (1) "Effect of excessive spins"

Typical electron spin resonance (ESR) spectrometer uses a microwave resonator, which is usually called a cavity, as a sensitive detector. A sample is usually set in the center of the cavity, and energy absorption by ESR phenomena is detected according to the degree of an impedance mismatching of the resonant circuit of the cavity. Absorption intensity in the ESR and FMR (Ferromagnetic Resonance) is proportional to the square root of the irradiated microwave power and the spin amount in the measured sample. Moreover, the spectral line width is proportional to the inverse of the transverse relaxation time of spins. The cavity is a device that stores only the light, of which the frequency is 𝜔𝑐=2𝜋𝑓𝑐, in the limited space. Electron spins lied in a static magnetic field are like spinning tops which are locked to specific Larmor frequency (𝜔𝑟=2𝜋𝑓𝑟). ESR/FMR spectrum is usually measured in the condition of 𝜔𝑐=𝜔𝑟. Recently, many attentions are gathering to the interaction between light (microwave) and spins in the cavity according to the development of quantum optics.

Strong interaction between light and electrons (3) "Strong coupling state of ferromagnetic thin film"

Coupling constant (𝑔𝑚) between microwave photon and electron spins is proportional to the square root of spin numbers as shown in eq.(1) of "Application Note ER200007E ". Therefore, FMR measurements using ferromagnets which include many spins and especially have narrow line widths do not work well, because spins in ferromagnets interact strongly with microwave photon, and achieve to "strong coupling" state larger than the state of "Purcell effect". Figure 1(a) is an example that shows the obtained unexpected spectrum in the strong coupling state. Normal FMR spectrum can be obtained as shown in Fig.1(d), if the filling factor is reduced and the system moves to a "weak coupling" state.

Analyses of the thermal characteristics and gaseous products of guanidine nitrate/basic copper nitrate mixtures using calorimetry with high resolution mass spectrometry

This work assessed the pyrolysis of a well-established gas generating agent consisting of a mixture of guanidine nitrate (GN) with basic copper nitrate (BCN), using thermogravimetry-differential scanning calorimetry in conjunction with high resolution mass spectrometry (TG/DSC/HRMS). This instrumentation simultaneously determined mass changes and heat flow, and also permitted evaluation of evolved gases on an accurate mass basis. Fragmentation ratio correction was used to analyze the MS data acquired via electron ionization. GN/BCN mixtures were found to undergo pyrolysis to evolve H2O, N2, NO, CO2 and N2O. Using HRMS, species having similar masses, such as CO2 and N2O, CO and N2, and NH3 and OH, were successfully distinguished. The thermal analysis data and the gas evolution results allowed a pyrolysis mechanism to be proposed. In this mechanism, a copper(II) complex obtained from the BCN catalytically decomposes NH3 generated from the GN to produce N2 and H2O. The pyrolysis of a mixture of GN and BCN thus provides a synergistic effect that increases the heat and gas output.

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Corona - Glow Discharge (DART Ion Source)

February 22, 2020
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