Table 1.

Fading of reflection spot intensities from 2D crystals at 80 K. Reported as ratio of diffraction spot fading N_e in ${\mathrm{e}}^{-}$/Å at 100/300 for C₄₄H₉₀ and purple membrane at different resolutions. Electron fluence N_e for diffraction spot intensities to fall to 1/e (the base of natural logarithms) of their initial diffraction intensity is on average 1.57  ±  0.03 times greater at 300 keV than at 100 keV. Measurements of fluence for various multiples m of 1/e and normalised by m in columns 4 and 5 to allowing direct comparison of N_e values with increasing damage.

Specimen	Resolution band (Å)	Multiple of 1/e	Ne 100 keV (${\mathrm{e}}^{-}/$Å2)	Ne 300 keV (${\mathrm{e}}^{-}/$Å2)	Ratio Ne(300 keV)/Ne(100 keV)
Paraffin	4	0.5	20.0	29.6	1.48
		1.0	13.3	21.5	1.61
		2.0	9.30	14.5	1.56
Purple	9	0.5	14.8	22.9	1.55
membrane		1.0	12.4	21.0	1.69
		2.0	10.9	–	–
	5	0.5	6.80	9.70	1.43
		1.0	5.72	8.65	1.51
		2.0	5.13	7.73	1.51
	4	0.5	5.50	9.64	1.75
		1.0	4.85	7.77	1.60
		2.0	4.20	7.02	1.67
Average					1.57 ± 0.03