D. Strasser

Electrostatic ion beam trap for electron collision studies

We describe a system combining an ion beam trap and a low energy electron target in which the interaction between electrons and vibrationally cold molecular ions and clusters can be studied. The entire system uses only electrostatic fields for both trapping and focusing, thus being able to store particles without a mass limit. Preliminary results for the electron impact neutralization of C2− ions and aluminum clusters are presented.

An affective disorder in zebrafish with mutation of the glucocorticoid receptor

Upon binding of cortisol, the glucocorticoid receptor (GR) regulates the transcription of specific target genes, including those that encode the stress hormones corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone. Dysregulation of the stress axis is a hallmark of major depression in human patients. However, it is still unclear how glucocorticoid signaling is linked to affective disorders. We identified an adult-viable zebrafish mutant in which the negative feedback on the stress response is disrupted, due to abolition of all transcriptional activity of GR. As a consequence, cortisol is elevated, but unable to signal through GR. When placed into an unfamiliar aquarium (‘novel tank’), mutant fish become immobile (‘freeze’), show reduced exploratory behavior and do not habituate to this stressor upon repeated exposure. Addition of the antidepressant fluoxetine to the holding water and social interactions restore normal behavior, followed by a delayed correction of cortisol levels. Fluoxetine does not affect the overall transcription of CRH, the mineralocorticoid receptor (MR), the serotonin transporter (Serta) or GR itself. Fluoxetine, however, suppresses the stress-induced upregulation of MR and Serta in both wild-type fish and mutants. Our studies show a conserved, protective function of glucocorticoid signaling in the regulation of emotional behavior and reveal novel molecular aspects of how chronic stress impacts vertebrate brain physiology and behavior. Importantly, the zebrafish model opens up the possibility of high-throughput drug screens in search of new classes of antidepressants.

High resolution mass spectrometry using a linear electrostatic ion beam trap

Abstract We describe a new mass spectrometric technique that is based on the use of a linear electrostatic ion trap and a newly discovered self-bunching phenomenon. Ions are stored in the trap and their oscillation frequencies are determined by Fourier transform of their oscillation times. Using this system, we demonstrate that it is possible to simultaneously trap several masses and obtain their mass spectra with high resolution. The instrument is compared to time-of-flight mass, as well as to ion cyclotron resonance mass spectrometers.

Heats of Vaporization of Room Temperature Ionic Liquids by Tunable Vacuum Ultraviolet Photoionization

The heats of vaporization of the room temperature ionic liquids (RTILs) N-butyl-N-methylpyrrolidinium bistrifluorosulfonylimide, N-butyl-N-methylpyrrolidinium dicyanamide, and 1-butyl-3-methylimidazolium dicyanamide are determined using a heated effusive vapor source in conjunction with single photon ionization by a tunable vacuum ultraviolet synchrotron source. The relative gas phase ionic liquid vapor densities in the effusive beam are monitored by clearly distinguished dissociative photoionization processes via a time-of-flight mass spectrometer at a tunable vacuum ultraviolet beamline 9.0.2.3 (Chemical Dynamics Beamline) at the Advanced Light Source synchrotron facility. Resulting in relatively few assumptions, through the analysis of both parent cations and fragment cations, the heat of vaporization of N-butyl-N-methylpyrrolidinium bistrifluorosulfonylimide is determined to be DeltaH(vap)(298.15 K) = 195 +/- 19 kJ mol(-1). The observed heats of vaporization of 1-butyl-3-methylimidazolium dicyanamide (DeltaH(vap)(298.15 K) = 174 +/- 12 kJ mol(-1)) and N-butyl-N-methylpyrrolidinium dicyanamide (DeltaH(vap)(298.15 K) = 171 +/- 12 kJ mol(-1)) are consistent with reported experimental values using electron impact ionization. The tunable vacuum ultraviolet source has enabled accurate measurement of photoion appearance energies. These appearance energies are in good agreement with MP2 calculations for dissociative photoionization of the ion pair. These experimental heats of vaporization, photoion appearance energies, and ab initio calculations corroborate vaporization of these RTILs as intact cation-anion pairs.

An innovative approach to multiparticle three-dimensional imaging

An innovative technique for three-dimensional imaging is presented, which uses the ratio of intensities of a pair of two-dimensional images to extract timing information. The principal advantage of this method is the ability to measure position and time for an almost unlimited number of particles hitting the detector simultaneously. The detector is capable of subnanosecond time resolution and position resolution of about 50 mu m. The photodissociation of H-2(+) is used to demonstrate the capability of the detector

Tunable wavelength soft photoionization of ionic liquid vapors

Combined data of photoelectron spectra and photoionization efficiency curves in the near threshold ionization region of isolated ion pairs from [emim][Tf(2)N], [emim][Pf(2)N], and [dmpim][Tf(2)N] ionic liquid vapors reveal small shifts in the ionization energies of ion-pair systems due to cation and anion substitutions. Shifts toward higher binding energy following anion substitution are attributed to increased electronegativity of the anion itself, whereas shifts toward lower binding energies following cation substitution are attributed to an increase in the cation-anion distance that causes a lower Coulombic binding potential. The predominant ionization mechanism in the near threshold photon energy region is identified as dissociative ionization, involving the dissociation of the ion pair and the production of intact cations as the positively charged products.

Quantum control of photodissociation by manipulation of bond softening

We present a method to control photodissociation by manipulating the bond-softening mechanism occurring in strong shaped laser fields, namely by varying the chirp sign and magnitude of an ultrashort laser pulse. Manipulation of bond softening is experimentally demonstrated for strong-field (

Dissociative recombination and low-energy inelastic electron collisions of the helium dimer ion

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The kick-out mass selection technique for ions stored in an Electrostatic Ion Beam Trap

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Self-bunching induced by negative effective mass instability in an electrostatic ion beam trap

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