Intermolecular free volumes and intramolecular defects inn-alkanes

Spin probe dynamics in relation to free volume in crystalline organics from ESR and PALS: N-tridecane

“…The lower-T step starts at T b2 3, cr τ * ≅255 K followed by another step with further sharp change of the o-Ps lifetime at T b2 3 τ ¼269 K towards the increasing trend in region V up to the end temperature of the PALS measurement. The observed τ 3 value of about 2.0-2.1 ns at the first step in region IV is in accord with the previous results on the n-TRD [24,25]. Similarly, the second step effect is marked by the characteristic PALS temperature T b2 3 τ with the initial value of about 3.2 ns at the beginning region V and those above T b2 3 τ are in consistent with the previous results on the liquid n-TRD [29,30].…”

“…Five regions of distinct thermal behavior in both the τ 3 vs. T plot and the I 3 vs. T one can be distinguished being depicted as I-V or A-E, respectively. Basically, the τ 3 vs. T plot of n-TRD exhibits a discontinuous course with two-step effects in consistency with the previous observations on a series of odd-numbered n-alkanes ranging from C 11 up to C 30 [21][22][23][24][25]. The lower-T step starts at T b2 3, cr τ * ≅255 K followed by another step with further sharp change of the o-Ps lifetime at T b2 3 τ ¼269 K towards the increasing trend in region V up to the end temperature of the PALS measurement.…”

“…On the other hand, only several external probe studies of nalkanes [19][20][21][22][23][24][25][26][27], especially those using atomic-sized probe PALS technique were reported [21][22][23][24][25][26][27]. In a series of n-paraffins some regularities in the o-Ps annihilation parameters as a function of even or odd type were revealed [21][22][23][24][25].…”

“…In a series of n-paraffins some regularities in the o-Ps annihilation parameters as a function of even or odd type were revealed [21][22][23][24][25]. While simple one-stepwise PALS response associated with the melting process at T m typical for small molecular crystalline organic compounds was observed in shorter alkanes (n o9), for higher odd-and still higher even-numbered n-alkanes starting from n-undecane (C 11 H 24 ) up to n-dotriacontane (C 32 H 66 ) an additional step just below this main one was detected and ascribed to the "rigid" solid to the "rotator" crystalline solid transition [21][22][23][24][25]. Moreover, the I 3 parameter also exhibits rich and complicated behavior below T m [21,26,27].…”

Positronium in solid phases of n-alkane binary mixtures

“…Alkanes and their mixtures are widely distributed in the natural environment; they are the main constituents of oil, lubricants, they appear as the building components of lipids, surfactants and liquid crystals. So far they have been the object of numerous studies by X-ray diffraction [1][2][3][4], DSC [1,[5][6][7], infrared and Raman spectroscopy [1,8,9], neutron scattering [10], positron annihilation [11][12][13][14][15] etc. If n < 25, only two solid phases of these compounds are observed: a rigid crystal and a waxy rotator phase.…”