Bijvoet's method, which makes use of anomalous x-ray diffraction or dispersion, is the standard means of directly determining the absolute (stereochemical) configuration of molecules, but it requires crystalline samples and often proves challenging in structures exclusively comprising light atoms. Herein, we demonstrate a mass spectrometry approach that directly images the absolute configuration of individual molecules in the gas phase by cold target recoil ion momentum spectroscopy after laser ionization-induced Coulomb explosion. This technique is applied to the prototypical chiral molecule bromochlorofluoromethane and the isotopically chiral methane derivative bromodichloromethane.

Ascertaining the physical state of a system is vital in order to understand and predict its behaviour. However, due to their fragile nature, the direct observation of quantum states has been elusive until recently. Historically, determination of the quantum state has been performed indirectly, through use of tomography. We report on two experiments showing that an alternative approach can be used to determine the polarisation quantum state in a simple, fast, and general manner. The first experiment entails the direct measurement of the probability amplitudes describing pure polarisation states of light, the first such measurement on a two-level system. The second experiment entails the direct measurement of the Dirac distribution (a phase-space quasi-probability distribution informationally equivalent to the density matrix), demonstrating that the direct measurement procedure is applicable to general (i.e., potentially mixed) quantum states. Our work has applications to measurements in foundational quantum mechanics, quantum information, and quantum metrology.Measurement plays a vital role in the practice of science. This is especially so in the case of quantum mechanics, where the measurement process is fundamental to the formulation of the theory. A crucial feature of quantum mechanics is that a measurement of one variable of a system erases information about the corresponding conjugate variable. The classic example is that determining the position of a particle disturbs its momentum, and vice versa. These measurements, known as strong measurements, collapse the wavefunction such that no additional information can be obtained.In order to completely determine a quantum state, which is described in general by complex numbers, one must perform multiple measurements on many identical copies of the system. Quantum tomography 1 is one method of quantum state determination that uses strong measurements 2-6 . Tomographic reconstruction entails estimating the complex numbers that describe the state

X-ray harmonics made with long-wavelength lasers reach higher fluxes and photon energies when plasma effects dominate.

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