Electron inelastic mean free path in water

Abstract

<p>A nanochannel liquid cell was used to quantify the electron inelastic mean free path (<italic>λ</italic>_IMFP) in water. The experimental values show large offsets from the generally accepted models, and can be used to determine the liquid thickness in a liquid cell.</p>

Mapping and Controlling Liquid Layer Thickness in Liquid‐Phase (Scanning) Transmission Electron Microscopy

“…We benchmarked our method with EELS thickness measurements on a water‐filled liquid cell, employing the standard theoretical model [ 34,35 ] (Figure 1f) and employing a very recent approach [ 36 ] that is based on an adjusted average energy‐loss term (Figure S9, Supporting Information). Our thickness measurements fall between both EELS approaches with our maximum liquid thickness being very close to the standard theoretical model and at lower thicknesses better matching the recent approach.…”

Nanofluidic chips for cryo-EM structure determination from picoliter sample volumes

“…The known total SiN thickness of 19 nm from ellipsometry measurements was used to calibrate the mean free path for inelastic scattering of silicon-rich nitride to 163 nm at 300 kV. We assumed a literature value of 320 nm (28) for the mean free path of vitreous ice. The derived quantity ‘water-equivalent thickness’ ( WET ) is the thickness of water/vitreous ice that would lead to the same I/I 0 , and is computed as follows: …”

“…1e]. From the zero-loss log ratio of a SiN x area adjacent to the nanochannel (0.89) and the geometric film thickness determined by ellipsometry (19 nm, corresponding to the combined thickness of top and bottom membrane), we calculated the mean free path for inelastic scattering (IMFP) at 300 keV in SiN x as 163 nm, from which we estimate a combined water-equivalent thickness of 39 nm for the two SiN x membranes forming the nanochannel assuming an IMFP of 320 nm for vitreous ice (28). We next mapped the apparent and absolute ice thickness at each image position.…”

Benchmarking ideal sample thickness in cryo-EM using MicroED

“…The inelastic mean free path (MFP) refers to the typical distance a high-energy electron travels through a specimen before losing energy, or inelastically scattering. In cryo-EM, the MFP is often used to compare samples of different thicknesses across different accelerating voltages (6, 7). The MFP in cryo-EM may be roughly calculated for a given sample, and has been investigated experimentally in vitreous ice, since this is the most probable environment in these experiments, though similar values have recently been demonstrated in liquid water (7, 8).…”

“…In cryo-EM, the MFP is often used to compare samples of different thicknesses across different accelerating voltages (6, 7). The MFP in cryo-EM may be roughly calculated for a given sample, and has been investigated experimentally in vitreous ice, since this is the most probable environment in these experiments, though similar values have recently been demonstrated in liquid water (7, 8). The calculated MFP for a typical protein crystal at accelerating voltages of 120, 200 or 300kV would correspond to roughly to 214, 272 and 317 nm, respectively (Materials and Methods).…”