On Nuclear Magnetic Relaxation in Dilute Gases of Symmetric and Spherical Top Molecules

Inert fluorinated gas T1 calculator

“…where I 0 is the moment of inertia of the molecule, ⁄ is PlankÕs constant, C i and s 1 , and C a and s 2 , are isotropic and anisotropic coupling constants and correlation times, respectively, x I and x J are nuclear and molecular Larmor precession frequencies, respectively, T is absolute temperature, and k B is BoltzmannÕs constant ( [13], from [10,[23][24][25][26][27]). It is commonly assumed that s 1 = s 2 " s because they both arise from molecular collisions.…”

“…There have been measurements of coupling constants and collision cross sections [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] that clearly lay out the physical framework, but to calculate a given T 1 often requires determining whether the desired range of physical parameters has been explored, sifting through different parameterizations of relaxation equations, and interpolating between tabulated parameters, after which it can be difficult to calculate the accuracy of the result. We present a unified calculation for common laboratory conditions so that a computer program will generate T 1 within a known accuracy if given pressure, temperature, and mixture composition.…”

“…We begin with the work of Courtney and Armstrong [13], whose physically motivated equations for fluorinated gases came explicitly from [10,[23][24][25][26][27]. In [13], the molecular collision dynamics were subsumed into a hard-sphere collision cross section parameter that was endowed with a nonlinear temperature dependence.…”

Measuring nanopore size from the spin–lattice relaxation of CF4 gas

“…The NMR relaxation of fluorine nuclei in gases such as SF 6 , SiF 4 , CF 4 , and C 2 F 6 is dominated by spin-rotation interaction, which is mediated by the molecular collision frequency [1][2][3][4][5][6][7][8]. When these gases are confined in pores of the order of the bulk gas mean free path, the frequency of collisions with the pore walls should rival that of intermolecular collisions and the NMR relaxation should be strongly affected [9].…”