The Role of the Unconscious in the Perception of Risks

Dr. Fritzsche argues that our world is too rational and that the psychology of the unconscious, as developed by Jung, can be key to understanding responses to hazards and to resolving conflicts that arise in the political management of risks

The Moral Dilemma in the Social Management of Risks

Dr. Fritzsche offers data seen as demonstrating that irrational fears can lead to grotesque imbalances in social efforts devoted to preventing fatalities

Atom-at-a-time laser resonance ionization spectroscopy of nobelium

International audienceOptical spectroscopy of a primordial isotope has traditionally formed the basis for understanding the atomic structure of an element. Such studies have been conducted for most elements1 and theoretical modelling can be performed to high precision2, 3, taking into account relativistic effects that scale approximately as the square of the atomic number. However, for the transfermium elements (those with atomic numbers greater than 100), the atomic structure is experimentally unknown. These radioactive elements are produced in nuclear fusion reactions at rates of only a few atoms per second at most and must be studied immediately following their production4, which has so far precluded their optical spectroscopy. Here we report laser resonance ionization spectroscopy of nobelium (No; atomic number 102) in single-atom-at-a-time quantities, in which we identify the ground-state transition 1S0 1P1. By combining this result with data from an observed Rydberg series, we obtain an upper limit for the ionization potential of nobelium. These accurate results from direct laser excitations of outer-shell electrons cannot be achieved using state-of-the-art relativistic many-body calculations5, 6, 7, 8 that include quantum electrodynamic effects, owing to large uncertainties in the modelled transition energies of the complex systems under consideration. Our work opens the door to high-precision measurements of various atomic and nuclear properties of elements heavier than nobelium, and motivates future theoretical work