To test the feasibility of determining defocus and astigmatism within

To test the feasibility of determining defocus and astigmatism within the error limits discussed above from the diffractogram of the side band image I used the tool CTFIT from the EMAN1 package [9]. Based only on the first zero I determined a defocus of about 195nm and an additional defocus in the y-direction of about 45nm (rather than 200 and 40nm). I did not try to evaluate the accuracy of the direction of astigmatism. Obviously, due to the nature of the diffractogram, it\’s not possible to use an existing automatic procedure for determining the CTF-parameters.

I present a novel design for a single side band aperture which allows determining defocus and astigmatism from the recorded images. I present the image formation theory and a method of correcting the transfer function of such an imaging system and test both in simulations. One clear advantage of single side band imaging is that the modulus of the complex valued transfer function is 1 for all spatial frequencies (outside the gaps). This means that images can be recorded at an arbitrary defocus value without introducing zeros in the transfer function. Therefore single side band imaging with such an aperture could be very suitable for imaging small proteins (100kDa and below). Thus this imaging mode could be an attractive alternative to imaging with phase plates.


Strongly correlated MLN4924 materials exhibit various intriguing and drastic phenomena such as the metal-insulator transition, high- superconductivity, and colossal/giant magneto resistance [1]. When multiple phases are adjacent and competing in the vicinity of a first-order phase transition for instance, there emerges self-organized electronic inhomogeneity with various types and length scales [2]. In order to find deeper insight into the macroscopic phenomena in these materials, it is indispensable to understand local electronic structures with relevant spatial resolution.
Scanning photoemission microscopy (SPEM) is one of the primary spectroscopic techniques for studying electronic states with spatial inhomogeneity [3]. Recently, this type of instrument has been developed to incorporate the capabilities of angle-resolved photoemission spectroscopy (ARPES), mainly at third-generation synchrotron facilities, often referred to as µ-ARPES or nano-ARPES [4–6]. These techniques have successfully revealed various electronic inhomogeneities in strongly correlated electron materials, such as metallic and insulating phase separation with a length scale of 10 µm in Cr-doped V2O3[7], electronic and structural inhomogeneities with a length scale of 100 µm in high- cuprate YBa2Cu4O8[8] as well as bilayer manganites LaSrMn2O7[9]. However, it is often inevitable to lower energy resolution to get higher count rates since photon flux is considerably reduced to achieve high spatial resolution due to low efficiency of focusing optics.
On the other hand, a major focus of conventional ARPES has been to study the density-of-states, band-dispersions, and Fermi surfaces of solids [10]. Modern ARPES with high energy and momentum resolutions, usually referred as high-resolution ARPES, can precisely determine quasiparticle\’s dispersion relations and lifetimes [11,12]. However, detailed microscopic information in the smaller area has not been sufficiently pursued by means of high-resolution ARPES so far.
By maximizing the merits of high energy and spatial resolutions, we have developed a new laser-based µ-ARPES system at the Hiroshima Synchrotron Radiation Center (HiSOR). High brilliance and monochromaticity of laser light is suited for high-resolution ARPES [13–15], and furthermore, its spatial coherence/directionality can be applicable to SPEM. In this paper, we present the design and typical performance of our µ-ARPES system equipped with a vacuum ultraviolet (VUV) laser tunable from 5.90 eV to 6.49 eV. Based on considerations on the commercially achievable specifications of laser light source, optics and focusing systems, we realized the compatibility with high spatial resolution better than 5 µm as well as the state-of-the-art energy and momentum resolutions. We have also examined spatial dependence of fine spectral features, which enables us to find sample area suitable for obtaining intrinsic electronic states. Present µ-ARPES holds the promise for uncovering intrinsic and fine details of electronic features that may have been overlooked by conventional high-resolution ARPES.