Biological membrane is composed of lipid molecules, because of its fluidity, it is possible to carry out physiological functions. Therefore, it is important to study the hydrodynamic properties of membranes toward understanding its function. Here, we observed the dynamical behavior of a lipid monolayer on the water surface under Marangoni flow. By using X-ray reflectometry, we obtained the tilt angle of the hydrocarbon chains of the lipid at different surface pressures. Comparing them with the dynamical surface pressure under Marangoni flow, it was found that the lipid molecules in rotational rather than translational motion. At low surface pressure, the molecular tilt angle is reduced by 20 degrees, even though the molecular area is reduced by at most 10%.

Regularly recurring phenomena are a common and important part of life. Such rhythmic behaviors are often seen in nonliving systems under far-from-equilibrium conditions. The study of simple nonliving systems provides clues for improving our understanding of the origin of biological rhythms. Here, we focus on the spontaneous oscillation of surface tension associated with an intermittent Marangoni convective flow generated by two types of surfactants, those that are partially soluble (long chain alcohols) and insoluble (lipids) in water. In this system, we find that the collective motions of two surfactants interact with each other in a systematic manner to control a stable periodic motion: The alcohol molecules (donor) produce a Marangoni flow, and the lipid molecules (acceptor) in a monolayer push the flow back. The shape of the surface tension oscillation can be explained by the viscoelastic properties of the acceptor surfactant, whereas the period of the surface tension oscillation has been explained by the physical properties of the donor surfactant. A recently developed time-resolved X-ray surface scattering technique enables the dynamic structure of the water surface under flow to be determined. We have repeatedly observed that lipid molecules at the air-water interface become regularly oriented normal to the surface at every onset of the Marangoni convective flow.

We present the results of time-resolved X-ray reflectivity measurements carried out to investigate the early stage of protein adsorption and deformation at an air-water interface. Three globular proteins [lysozyme, myoglobin, and bovine serum albumin (BSA)] were studied, and we observed that the proteins adsorbed at the air-water interface initially possessed a thinner conformation than their native structures. The degree of deformation increased in the order myoglobin < lysozyme < BSA, which was inconsistent with the order of molecular flexibility. The initial rate of protein adsorption increased in the order lysozyme < BSA < myoglobin as determined by the dynamic surface tension. More flexible proteins generally adsorb at the interface more rapidly however, proteins with hydrophobic patches on the protein surface, such as myoglobin, adsorb at the interface with little deformation. These results provide evidence that protein unfolding during adsorption only takes place if the kinetics of adsorption are similar to or slower than the kinetics of unfolding.

An X-ray reflectometer using a laboratory X-ray source for quick measurements of the specular X-ray reflectivity curve is presented. It uses a bent-twisted crystal to monochromatize and focus the diverging X-rays (Cu K alpha(1)) from a laboratory point source onto the sample. The reflected X-rays are recorded with a two-dimensional detector. Reflectivity curves can be measured without rotating the sample, detector or X-ray source during measurements. The instrument can separate the specularly reflected X-rays from the diffuse scattering background, so low reflectivities can be measured accurately. For a gold thin film on silicon, the reflectivity down to the order of 10(-6) was obtained with a measurement time of 100 s and that down to 10(-5) with a measurement time of 10 s. Reflectivity curves of a silicon wafer and a liquid ethylene glycol surface are shown as well. Time-resolved measurements of a TiO2 surface during UV irradiation are also reported.

Hofmeister anion effects on adsorption kinetics of the positively charged lysozyme (pH < pI) at an air-water interface were studied by surface tension measurements and time-resolved X-ray reflectometry. In the salt-free solution, the protein adsorption rate increases with decreasing the net positive charge of lysozyme. When salt ions are dissolved in water, the protein adsorption rate drastically increases, and the rate is following an inverse Hoffmeister series (Br- > Cl- > F-). This is the result of the strongly polarized halide anion Br- being attracted to the adsorbed protein layer due to strong interaction with local electric field, while weakly polarized anion F- having no ability to penetrate the protein layer. In X-ray reflection studies, we observed that the lysozyme molecules initially adsorbed on the air-water interface have a flat unfolded structure as previously reported in the salt-free solution. In contrast, in the concentrated salt solutions, the lysozyme molecules begin to refold during adsorption. This protein refolding as a result of protein-protein rearrangements may be a precursor phenomenon of crystallization. The refolding is most significant for Cl-, which is a good crystallization agent, whereas it is less observed for the strongly hydrated F-. It is widely known in the bulk state that kosmotropic anions tend to precipitate proteins but at the same time stabilize proteins against denaturing. On the other hand, at the air-water interface where adsorbed proteins usually unfold, we observed chaotropic anions strongly bound to proteins that reduce electrostatic repulsion between protein molecules, and subsequently they induce protein refolding whereas the kosmotropic anions do not.

Protein unfolding at an air-water interface has been demonstrated such that the X-ray reflectivity can be measured with an acquisition time of 1 s using a recently developed simultaneous multiple-angle-wavelength-dispersive X-ray reflectometer. This has enabled the electron density profile of the adsorbed protein molecules to be obtained in real time. A globular protein, lysozyme, adsorbed at the air-water interface is found to unfold into a flat shape within 1 s.

The density profiles of lysozyme layers at the air-water interface before and after adding salt were determined by X-ray reflection. After adding salt, the density of the lysozyme (LSZ) layers decreases, whereas the thickness drastically increases. The salt ions are considered to increase the LSZ-LSZ interaction, and consequently decrease the surface activity of LSZ, allow adsorbed lysozyme molecules crystallize. (C) 2013 Elsevier B. V. All rights reserved.

X-ray reflectivity measurements were applied to hexadecane wetting film on aqueous solutions of hexadecyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB). In both cases, the monolayers in which oil molecules are penetrated from hexadecane droplets into surfactant-adsorbed films were found at room temperature. Upon cooling, they showed first-order freezing transitions, however, it was also confirmed that the structures of freezing films were qualitatively different: hexadecane molecules were frozen together with CTAB to form mixed solid monolayer in CTAB-hexadecane while the frozen hexadecane monolayer wetted mixed liquid monolayer in TTAB-hexadecane.

X-ray reflectivity is a non-destructive characterization technique for thin films. Either solids or liquids, inorganic or organic compounds can be analyzed. Although this technique has the disadvantages that relatively wide and flat samples are necessary, they are overcome by using synchrotron radiation sources. In this article, characterization of protein layers bound to supported lipid bilayers and time-resolved measurements for protein layers formed on a water surface are shown for examples.

The whole profile of the specular X-ray reflectivity curve was simultaneously and quickly measured with no need to rotate the specimen, the detector or the monochromator crystal. A white synchrotron beam from a bending magnet source is incident on a bent-twisted silicon (111) crystal polychromator that produces a convergent X-ray beam with a continuously varying wavelength (energy) and glancing angle to the specimen surface. This convergent X-ray beam was specularly reflected in the vertical direction by the specimen placed at the focus. The normalized spatial distribution across the beam direction of the reflected beam represents a specular X-ray reflectivity curve because each position along the line recorded on the two dimensional detector surface corresponds to a different momentum transfer. Reflectivity curves from a (001) silicon wafer, a nickel thin film on a silicon substrate, and a water surface were measured with data collection times of 0.001-100 s, 0.01-100 s, and 1.0-1000 s, respectively. The simultaneously covered momentum transfer range was 0.03-0.52 Å-1 for solid specimens and 0-0.41 Å-1 for liquid specimen. © Published under licence by IOP Publishing Ltd.

An X-ray reflectometer has been developed, which can simultaneously measure the whole specular X-ray reflectivity curve with no need for rotation of the sample, detector or monochromator crystal during the measurement. A bent-twisted crystal polychromator is used to realise a convergent X-ray beam which has continuously varying energy E (wavelength lambda) and glancing angle alpha to the sample surface as a function of horizontal direction. This convergent beam is reflected in the vertical direction by the sample placed horizontally at the focus and then diverges horizontally and vertically. The normalized intensity distribution of the reflected beam measured downstream of the specimen with a two-dimensional pixel array detector (PILATUS 100K) represents the reflectivity curve. Specular X-ray reflectivity curves were measured from a commercially available silicon (100) wafer, a thin gold film coated on a silicon single-crystal substrate and the surface of liquid ethylene glycol with data collection times of 0.01 to 1000 s using synchrotron radiation from a bending-magnet source of a 6.5 GeV electron storage ring. A typical value of the simultaneously covered range of the momentum transfer was 0.01-0.45 angstrom(-1) for the silicon wafer sample. The potential of this reflectometer for time-resolved X-ray studies of irreversible structural changes is discussed.

The conformation of protein molecules is determined by a balance of various forces, including van der Waals attraction, electrostatic interaction, hydrogen bonding, and conformational entropy. When protein molecules encounter an interface, they are often adsorbed on the interface. The conformation of an adsorbed protein molecule strongly depends on the interaction between the protein and the interface. Recent time-resolved investigations have revealed that protein conformation changes during the adsorption process due to the protein-protein interaction increasing with increasing interface coverage. External conditions also affect the protein conformation. This review considers recent dynamic observations of protein adsorption at various interfaces and their implications for the kinetics of protein unfolding at interfaces.

The nanosecond pulsed laser ablation of a gold plate at the excitation wavelength of 532 nm was conducted in the supercritical fluid of dipolar trifluoromethane (CHF 3). The generation of gold nanoparticles was investigated as a function of the fluid density that corresponded to changes in the permittivity and thermal properties over the wide ranges. The analysis of data from electron microscopy and small-angle X-ray scattering (SAXS) revealed that the principal product is a gold nanonetwork with length up to a few 10 μm and a branched structure. The gold nanonetwork consisted of gold nanospheres with an average diameter of 20 nm and a mass fractal structure. The mass fractal dimension of the nanonetwork changed by the fluid density, and its dimension was attributed to the number of the nanospheres. It was clarified that not the fluid thermal properties but the ambient dielectricity and polarization energy during the ablation are responsible for the morphology and number of gold nanoparticles. This is the first report of (i) fractal structure of gold nanoparticles created by the ablation, (ii) ablation mechanism in dipolar and nondipolar fluids, and (iii) a chemical-free nanoparticle synthesis in a dipolar fluid. © 2012 American Chemical Society.

A protein salting-out process is directly observed at an air-water interface. By using time-resolved X-ray specular reflectivity and off-specular diffuse scattering, we identified several key stages in the adsorption of hen egg white lysozyme in a concentrated NaCl solution, (1) adsorption-induced unfolding, (2) monolayer formation with unfolded proteins, (3) protein refolding, and (4) island formation with the refolded proteins. Stages 3 and 4 are not observed either at the isoelectric point or in the salt-free solution, suggesting that they are induced by screening of the positive charges in the lysozyme by chloride ions. It is considered that the hydrated salt ions act to minimize the water-accessible surface area of the protein, not only enhancing protein dehydration (stages 1 and 2) but also assisting in protein refolding and association (stages 3 and 4). These results provide insight into the early stages of protein crystal nucleation.

Ultrasonic atomization, in general, generates mist of liquid droplets with the diameter of micrometer order. Recently, our measurements with small-angle X-ray scattering (SAXS) at SPring-8 have revealed that the droplets of 1 nm dominate the whole population of atomized mist of ethanol. This article describes the details of SAXS measurements and discusess the mechanisms of the nano-sized droplet generation.

An X-ray reflectometer for simultaneous measurement of specular and off-specular reflection of liquid surfaces is described. The reflectometer, equipped with a two-dimensional single X-ray photon-counting pixel array detector obtained the full range of X-ray specular and off-specular reflections in an extremely short time (1 s). Both the specular and off-specular reflection of water exhibited good agreement with the predicted capillary-wave theory within the appropriate instrumental resolution. The approach is also demonstrated on an aqueous solution of 1-dodecyl-3-methylimidazolium chloride. The monolayer in which the dodecyl chain faces upwards and the Cl- anion locates next to the imidazolium ring formed on the water surface was found to be laterally homogeneous. The use of a pixel array detector will be particularly powerful for in situ measurements to investigate both out-of-plane and in-plane structures simultaneously, not only for liquid surfaces but also for other thin films.

X-ray reflectivity measurements of liquid surfaces were demonstrated using a recently developed liquid interface reflectometer at SPring-8. The reflectometer, equipped with a two-dimensional hybrid pixel array detector (PILATUS), achieved x-ray reflectivity towards 10(-9) with an integration time at each angle of only 1 sec, offering enormous potential for rapid measurements. Time-resolved measurements at a time resolution of 1 min were performed on the adsorption process of a globular protein lysozyme on a water/air interface.

Time-resolved X-ray reflectivity measurements for lysozyme (LSZ) adsorbed at an air/water interface were performed to study the mechanism of adsorption-induced protein unfolding. The time dependence of the density profile at the air/water interface revealed that the molecular conformation changed significantly during adsorption. Taking into account previous work using Fourier transform infrared (FTIR) spectroscopy, we propose that the LSZ molecules initially adsorbed on the air/watcr interface have a flat unfolded structure, forming antiparallel P-sheets as a result of hydrophobic interactions with the gas phase. In contrast, as adsorption continues, a second layer forms in which the molecules have a very loose structure having random coils as a result of hydrophilic interactions with the hydrophilic groups that protrude from the first layer.

Grazing-incidence x-ray diffraction measurements were carried out to observe the surface structure of [bmim][PF6]. At an incident angle of less than the critical angle, a diffraction pattern from 10 nm beneath the surface was obtained. A broad Debye-Scherrer ring was observed in the diffraction patterns, indicating that the [bmim][PF6] molecules near the surface are randomly orientated, similar to those in the bulk liquid. The distance of the. nearest anions was estimated to be 4.2 angstrom, which is very close to that for bulk [bmim][I], suggesting that the liquid structure of [bmim][PF6] is determined by the packing of the cation.

Small-angle x-ray scattering measurements using a brilliant x-ray source revealed nanometer sized liquid droplets in a mist formed by ultrasonic atomization. Ultrasonic atomization of ethanol-water mixtures produced a combination of water-rich droplets of micrometer order and ethanol-rich droplets as small as 1 nm, which is 10(-3) times smaller than the predicted size. These sizes were also obtained for mists generated from the pure liquids. These results will help to clarify the mechanism of "ultrasonic ethanol separation," which has the potential to become an alternative to distillation. (C) 2007 American Institute of Physics.

X-ray reflectivity profiles of human lactoferrin absorbed at water interfaces have calculated using the structure determined by neutron reflection measurements [Lu et al., Langmuir, 21, 3354 (2005)]. A significant difference in the expected profiles was observed between the unfolding lactoferrin at the interfaces and aqueous subphase itself. Time-resolved X-ray reflectivity measurements are proposed to probe the protein adsorbing process at interfaces.

The surface structure of 2-butoxyethanol (BE)-water mixtures at 300 K was studied by x-ray reflection and surface tension measurements. It is striking that a finite intrinsic surface width attributed to the surface excess BE was observed only below BE mole fraction x(BE)=0.017 where the pseudophase transition occurs in the bulk. The monolayer formation at x(BE)approximate to0.005 was found from the result of a curve fitting to the measured reflectivities by using the density profile of a single-layer "box" model in which interfaces were smeared by thermal capillary waves. (C) 2002 American Institute of Physics.

We have constructed a grazing incidence x-ray reflection system for liquid-vapor interfaces by use of an imaging plate as an area detector. The reflectivity data were obtained with high resolution even by use of a conventional x-ray tube. The surface reflectivity measurements for pure water, ethanol and 2-butoxyethanol were performed and the values of the surface roughness were obtained as 4.1 +/- 0.1, 7.1 +/- 0.3 and 6.2 +/- 0.2 Angstrom, respectively. For water, slight broadening of reflection peaks was observed. This was caused by the surface curvature due to the large surface tension. By fitting the reflection profiles, the radius of curvature was found to be nearly 100 m for water and ten times larger for ethanol and 2-butoxyethanol. (C) 2000 American Institute of Physics. [S0021-9606(00)70321-7].

The structure of liquid chloroform has been investigated by energy-dispersive X-ray diffraction. For the stability of the sample thickness, even for a volatile liquid, a glass capillary tube has been used as a sample container. The intensity function has been accounted for by a bcc (body-centered cubic)-like local lattice structure model with a lattice constant of 6.24 Angstrom. However, it has been necessary to replace a fraction (34%) of the nearest neighbors by super-near configurations in which molecules are rather tightly correlated. The correlation is, however, rapidly lost as the distance between molecules increases, and the long range structure is characterized by a large Prins parameter. The structure of liquid chloroform is much less ordered than that of carbon tetrachloride.

生命活動には、心臓の鼓動や呼吸などのように、リズムを刻む現象が数多く見られます。このようなリズム運動は、非平衡な状態の中では非常に安定な定常状態として実現されています。今回我々は、このようなリズム運動の起源を探るために、マランゴニ対流発生に伴う表面張力の自発振動に着目しました。我々は、この振動現象が、2種類の界面活性剤が相互作用することによって起こっていることをつきとめました。また、最近開発した高速X線反射率測定装置によって、マランゴニ対流が発生するたびに、分子が規則的に並ぶことを見つけました。

本研究では、新たに実験室の白色X線を用いたエネルギー分散型X線反射率測定装置（ED-XRR）を製作し、それを現有の全反射赤外分光装置(FT-IR)と組み合わせて、液体/プリズム界面の構造をリアルタイムで検出するシステムを開発した。 ED-XRR装置を用いて10-5まで最短10秒でX線反射率測定が可能であることがわかった。また、5分でX線回折パターンも測定可能であることがわかった。 一方、タンパク質と塩の相互作用について、FT-IR単独測定による2次構造の追跡にも成功したが、ED-XRRとの同時測定はできなかった。しかしながら、X線回折との同時測定は可能であり、応用範囲は広いと思われる。

人工組織や生体物質を使った新しい機能性材料の開発など、医学的および技術的応用の両面においても生体物質と界面の相互作用を知ることは非常に重要である。昨年度は、X線反射率とその周囲に生じる微弱な散乱を精度良く計測することにより、タンパク質の界面垂直・水平方向の構造情報を同時に取得する手法を確立した。当該年度はこれを用いて様々な条件における球状タンパク質リゾチームの界面吸着過程を観測し、結果を体系化した。概要を以下にまとめる。 一般にタンパク質の界面吸着のドライビングフォースは、疎水性界面ならば疎水性相互作用、親水性界面ならば静電相互作用となり、前者は後者よりも大きなコンフォメーションの変化を引き起こす。また、母液の濃度が低いほど、界面吸着速度は遅くなり、より大きなコンフォメーションの変化を誘発する。 等電点よりも低いpHの場合は、リゾチームは正に帯電するため、リゾチーム同士の静電反発が大きくなって吸着速度は低下する。一方、等電点においては、吸着速度は増加するが、分子内の静電反発によって大きく変性する。イオン強度が大きくなると、リゾチーム同士の静電反発が遮蔽されるため、リゾチーム同士のファンデルワールス力が強くなる。 タンパク質の界面吸着のドライビングフォースは、吸着の初期段階ではタンパク質と界面の相互作用だけを考えれば良いが、界面被覆率が増加するに従って、タンパク質同士の相互作用が大きくなる。その結果、タンパク質のコンフォメーションは、吸着後も徐々に変化する。よって、このような変化を追跡できる測定法の開発は非常に重要である。

エタノール水溶液に超音波を照射してミスト化すると、ミストの中にエタノールが濃縮する。この超音波霧化分離は、発生するミストの粒径がナノサイズである場合に効率良く起こる。本研究では、最も分離効率の良い霧化条件を見つけるために、X 線小角散乱法によって霧化条件と発生するミストの粒径を相関づけたところ、ナノ液滴の発生を促進させるには3つの要因(1)溶液構造、(2)気液平衡、(3)供給エネルギー、があることがわかった。

アルキル鎖を持つイミダゾリウム塩【C_n mim】X(nは炭素数Xはハロゲン)は、アルキル鎖の長さが増すと界面活性剤としての性質が際立ってくる。n>6でミセル形成が観測されており、臨界ミセル濃度(cmc)はnと伴に低濃度側にシフトする。一方、同じ炭素数でアニオン種を変えた場合cmcはほとんど変わらないが、アニオン半径が大きくなるとミセル中の会合体数も多くなることが報告されている。水溶液中では、アルキル鎖同士の疎水性相互作用、カチオンとアニオンの静電相互作用、アニオンと水の水和が競合してミセル会合体を形成する。このような相互作用の寄与を分離するためには、水溶液中のミセルではなく共存する水溶液表面の分子膜の構造に着目したほうが良いと考え、本研究ではX線反射率測定を試みた。 その結果、臨界ミセル濃度付近の【C_n mim】X(n=8,12、X=Cl,Br)水溶液はアルキル鎖のパッキングが50%で、アニオンがイミダゾリウム環の隣に配置した表面単分子膜を形成していることがわかった。[C_12mim】Cl水溶液の場合は、濃度の増加に伴って、Crのポジションが表面近くに移動すること、[C_8mim]X水溶液の場合は、Br^-の方が表面に近く位置していることを考えると、アニオンのポジションはイミダゾリウム環の静電相互作用が最も支配的であるが、水和の影響をわずかに受けることがわかった。 一方、反射率測定の際に得られる散漫散乱強度を検討したところ、上の表面単分子膜が面内方向に非常に均一な膜であることがわかった。

X線反射率法(XR)とは、X線を試料に対してすれすれに入射させ、全反射角度近傍での反射率を観測することにより、表面深さ方向の密度分布を得ようというものである。入射角の-4乗で変化するX線強度を精度良く測定しなければならないため、分子レベルで構造を決定するには放射光源を用いるのが常套手段となっている。これまで国内の放射光施設には、そのような装置を備えたビームラインが存在しなかったが、本研究は、高輝度光科学研究センターの宇留賀らとともにSPring-8に溶液界面反射率計を立ち上げることに大いに貢献した。イオン液体についての測定にはまだ至っていないが、測定時間わずか2分というこの装置は、水溶液表面にイオン液体が吸着する過程といったダイナミクス研究に威力を発揮すると思われる。 一方、反射X線の周囲に生じる回折像(表面X線回折、GIXD)を解析すると、水平面内の構造情報も得ることができる。本研究では実験室の反射率計を用い、X線の入射角を制御して表面深さ10nmの回折パターンを得ることに成功した。ニートなイオン液体のGIXD測定を行ったところ、[bmim]PF_6表面の回折パターンは、片柳らが報告したバルクの[bmim]I片柳らが報告したバルクの[bmim]Iのパターンと非常に良く似ており、表面構造はカチオンが支配していることがわかった。一方、[bmim]TFSIのパターンは全く異なっており、かさ高いアニオンが構造を支配していることがうかがえる。

イオン液体とは常温で液体状の有機塩である。極性が高く低粘度である上に、分子構造を少し変えることによって物性を変えることができるため、デザイナブル液体として多方面にわたって注目を浴びている。イオン液体が常温で液体である理由は、複雑な分子構造とイオンまたは特定の官能基(あるいは原子)間の相互作用にある。すなわち、イオン間に働く力が静電的なクーロン力だけでなく、水素結合があることが無機の溶融塩と大きく異なる点である。本研究では、その複雑な相互作用を解明することが目的である。近年、我々はX線反射率測定を用いてアルコール水溶液の表面構造を研究したところ、表面構造とバルクの構造には密接な相関があることがわかった。そこで、本研究では表面構造研究からイオン液体中の相互作用を理解することを試みた。平成16年度は現有のX線反射率測定装置でイオン液体[bmim]BF4の測定を行った。その結果、最高角1.8度で層構造を示唆する強度の増加が観測されたが、表面構造を決めるためには、さらに高角度の反射をとらなければならないことがわかった。ところが反射強度は入射角の-4乗で減衰するので、現有のX線源では強度が弱すぎて、測定することができない。そこで、平成17年度はは今まで使っていたGe111モノクロメータの代わりに人工多層膜モノクロメータに変更するために、反射率測定装置の大幅な改良を行った。その結果、従来の25倍の強度を得ることができた。液体グリセリンを使って性能評価したところ、従来検出器にイメージングプレートを用いて1週間かかっていた測定が、シンチレーションカウンタを用いて2時間で測定することが可能になった。今後は改良した装置を用いてイオン液体表面の構造研究を行う予定である。

2-ブトキシエタノール(BE)水溶液は、モル分率0.07、約50℃で2相分離を起すことが知られている。常温においては1相であるが、ミクロな混合状態が異なる3つの濃度領域(27℃では、モル分率0<領域I<0.017

「気-液界面構造研究のためのX線反射率測定装置」を製作した。反射率測定では、X線が試料に対してすれすれに入射する非常に低角の角度領域で、大幅な強度変化を正確にとらえる必要があり、装置として要求される性能は、(1)測角精度の高いゴニオメータを備えていること、(2)入射X線の平行性と単色性が良いこと、(3)入射X線ビームは幅が狭く、高強度であること(4)X線検出器は低バックグラウンドで高計数率対応型であることが挙げられる。我々が製作した試料水平型X線反射率測定装置は、大別すると、3つのパ-ツ(光源、試料周辺、検出部)で構成されている。主な特色は、(1)ゴニオメータに5相ステッピングモータによる自動ステージを採用し、(2)Ge(111)結晶を(3)非対称カットしたものをモノクロメータ用いている。さらに画期的なことは、(4)検出器に2次元ディテクターであるイメージングプレートを用いることで、X線源に2.2KW封入管を用いているにもかかわらず、従来にない高精度な測定が簡単なアラインメントで実現可能になった。また、この装置を気-液界面に応用するにあたり、液面の振動および蒸発による位置変化が問題となったが、試料を自動ステージに載せ、高さを蒸発速度に合わせて上げることで解決した。さらに、同条件下で表面張力を測定できるように、輪環法による自動表面張力測定装置を製作し、反射率測定装置に組み込んだ。 このX線反射率測定装置の性能評価にあたり、水のX線反射測定を行ったところ十分精度の高い測定結果を得ることができた。また、数種のアルカノールについて測定を行い、分子の形と気-液界面層の厚さの関係について研究した。さらに、2-ブトキシエタノール水溶液の表面張力測定を行い、表面付近での溶質の過剰量と溶液内部における混合状態の相関について議論した。