A general soft ionization method for mass spectrometry: Resonance-enhanced multi-photon ionization of biomolecules

We show here that ‘double-barrelled’ laser desorption/resonance-enhanced multi-photon ionization mass spectrometry has many advantages over traditional single-step desorption/ionization techniques, particularly if combined with Reflectron-Time-of-Flight mass analysers. We demonstrate the effectiveness of this technique for large labile biomolecules, namely native chlorophylls, porphyrins and a peptide, as examples of structural and mass analysis.     

Intensity and lifetimes of ZEKE spectra

The questions addressed in this Letter are whether the lifetime or intensity of long-lived molecular ZEKE/Rydberg states are influenced by the intensity of background ions and hence whether these background ions are mechanistically involved in the formation of ZEKE states. We performed an experiment changing the ion density which had no appreciable effect on the intensity of the ZEKE signal. ZEKE states with a lifetime of many tens of microseconds are here not changed by background ions, either in lifetime or intensity.     

Theory of time-resolved level anticrossing experiment

The purpose of the present paper is to present a general treatment of steady state and time-resolved level-anticrossing (LAC) experiments using the generalized master equation approach in which both radiate and nonradiative decays and dephasing processes have been considered. Several models are treated to demonstrate the theoretical method. The theory is applicable to both atoms and molecules. It is shown that under appropriate conditions, as derived in this paper, quantum beats can be observed in the time-resolved LAC experiment. Numerical calculations have been performed to show the time-dependent behavior (build-up and decay) of the time-resolved LAC experiment. These quantum beats are then a direct measurement of the microscopic coupling parameters in intersystem crossing, etc. It will be shown that combining the steady state and the time-resolved LAC experiments one can determine not only the microscopic coupling parameters but also the relaxation and/or the dephasing rate constants. Hence the particular virtues of time dependent LAC experiments are seen in these model calculations.     

Selected fluorescence and dissociation lifetimes on N2O+ in its Ã(2Σ+),000 and 100 states

Radiative and radiationless lifetimes together with the quantum yield towards fluorescence of individual vibronic states of molecular ions can be determined by threshold electron—fluorescence photon coincidence measurements. This method is here applied to the X?²Π_{$\text{3}\text{2,1,2}$} and òΣ⁺ states of N₂O⁺ which were also studied by high resolution photoionization resonance spectroscopy.     

Dispersive Estimates for Schrödinger Operators in Dimensions One and Three

We consider L¹L estimates for the time evolution of Hamiltonians H=–+V in dimensions d=1 and d=3 with bound We require decay of the potentials but no regularity. In d=1 the decay assumption is (1+|x|)|V(x)|dx<, whereas in d=3 it is |V(x)|C(1+|x|)^–3–.Supported by the NSF grant DMS-0070538 and a Sloan fellowship.     

Threshold Phenomenon for the Quintic Wave Equation in Three Dimensions

For the critical focusing wave equation ${\square u = u^5 \, {\rm on} \, \mathbb{R}^{3+1}}$ in the radial case, we establish the role of the “center stable” manifold ${\Sigma}$ constructed in Krieger and Schlag (Am J Math 129(3):843–913, 2007) near the ground state (W, 0) as a threshold between blowup and scattering to zero, establishing a conjecture going back to numerical work by Bizoń et al. (Nonlinearity 17(6):2187–2201, 2004). The underlying topology is stronger than the energy norm.