Daniel Wolf Savin - Senior Research Scientist
Email:	savin@astro.columbia.edu
Office:	1210C Pupin Physics Laboratories
Office Phone:	1 - 212 - 854 - 4124
Office Fax:	1 - 212 - 854 - 8121
Lab Phone:	1 - 914 - 591 - 2874
Lab Fax:	1 - 914 - 591 - 4906
Home:	1 - 212 - 316 - 2627
Germany:	49 - (0)1520 - 562 - 1649
Israel:	972 - (0)54 - 756 - 7391

Group Members Present and Past
Postdocs
Hjalmar Bruhns (08/2006-present)	Paul Bryans (10/2005-present)
Holger Kreckel (03/2007-present)	Michael Lestinsky (07/2007-present)
Dragan Lukić (02/2005-08/2007)	Michael Schnell (04/2004-03/2006)
Bohdan Seredyuk (02/2006-12/2007)
Long Term Visitors
Julian Berengut (09/2007-04/2008)	Holger Kreckel (7/2006-9/2006)
Graduate Students
Tony Mroczkowski (2001-2002)
Undergraduate Students
Warit Mitthumsiri (Summer 2004-Spring 2007)	Benjamin L. Schmitt (Summer 2008)
Adam Shapiro (Spring 1999)

Job Openings:
   Postdoctoral Research Scientist in Experimental Atomic and Molecular Physics

CV: pdf format

Publications

Selected Research Interests:
   Formation of protogalaxies and the first stars in the early universe
   Cosmic origins of organic chemistry
   Winds from supermassive black holes
   Characterizing the origins of the solar wind

Formation of protogalaxies and the first stars in the early universe:

During the epoch of first star and protogalaxy formation the formation of these structures was mediated through H₂ which is an important coolant in primordial clouds. The dominant formation mechanism of H₂ during this epoch is the associative detachment (AD) reaction H^- + H → H₂ + e^-. Published values for this process differ by nearly an order of magnitude. This introduces uncertainties into cosmological models of structure formation. Our recent modeling studies have shown that the effect is particularly large for protogalaxies forming in previously ionized regions, affecting predictions of whether or not a given protogalaxy can cool and condense within a Hubble time, and altering the strength of the ultraviolet background that is required to prevent collapse.

To study this AD reaction in the laboratory, we begin with an anion beam and use photodetachment to generate a self-merged, anion-neutral beams arrangement. Laboratory beam energies are in the keV range. Because the beams are co-propagating, center-of-mass energies from the meV to keV range will be achievable. We will observe the AD reaction by detecting fast H₂⁺ ions formed through ionizing collisions of the AD-generated H₂ with the background gas in the vacuum chamber.

Cosmic origins of organic chemistry

There is a growing consensus that the cosmic pathway to life begins not on planetary surfaces, but in interstellar gas clouds where atomic carbon is ``fixed'' into molecules, thereby initiating the synthesis of the complex organic species that are eventually sequestered on planets. Tracking these processes requires cross-disciplinary work at the intersection of astronomy, chemistry, biology, and physics. Much of our knowledge of this pathway derives from radio-frequency spectroscopy of molecular clouds which require sophisticated astrochemical models to interpret the observations. However, breakthroughs in our understanding of the molecular universe are limited by uncertainties in the underlying chemical data in these models. Of particular importance are data for reactions of neutral atomic carbon atoms with molecular ions which are critical in initiating interstellar organic chemistry. Theory is limited to classical methods as fully quantum mechanical reactions for systems with four or more atoms are beyond computational capabilities now and for the foreseeable future. Existing laboratory experiments have produced ambiguous results owing to the extraordinary challenge of generating and characterizing atomic carbon beams.

There has never been greater urgency for the resolution of these problems. Within 5-10 years other Earth-like planets will have been found and characterized, yet our ability to place these worlds in proper context will be hampered unless we can complete our understanding of the chain of events that dictates their potential chemical inventories. Development of a new experimental technology enabling experimental studies previously not possible is urgently required to address the cosmic origins of organic chemistry. To study these first links in the chemical chain leading towards life, we propose to develop a unique laboratory instrument using photodetachment of C^- to produce C beams, merging the resulting C beam with various molecular ions, and studying the end products. Our approach will not suffer from the limitations of previous experimental methods.

Winds from supermassive black holes:

Recent X-ray satellite spectroscopic observations by Chandra and XMM-Newton of active galactic nuclei (AGNs) have detected a previously unobserved set of spectral features. These features are attributed to the winds emanating from the supermassive black hole lurking in the center of each AGN. However, our ability to reliably interpret these features to infer the properties of this wind and the embedded black hole is limited by uncertainties in our understand of the atomic physics which produces the observed spectrum. Of particularly importance is determining correctly the ionization structure of the gas. This in turn depends on understanding the electron-ion recombination process known as dielectronic recombination (DR).

To study the relevant recombination processes, my group and our collaborators at the Max Planck Institute for Nuclear Physics (MPIK) and the University of Giessen, Germany, are carrying out a series of DR measurements. The efforts of my collaborators are being led by Prof. Dr. Andreas Wolf at MPIK and Prof. Dr. Alfred Müller at Giessen. Measurements are carried out using the heavy-ion test storage ring (TSR) at the MPIK in Heidelberg, Germany.

Characterizing the origins of the solar wind:

Investigating the dynamics of the solar corona is crucial if one is to understand fundamental solar and heliospheric physics. The corona also greatly influences the Sun-Earth interation as it is from here that the solar wind originates. The solar wind can have a profound effect on the Earth's magnetosphere and ionosphere, disrupting power grids and commmunication. Hence characterizing the origins of the solar wind is of obvious importance. This is done, in part, through a combination of solar spectroscopic observation, spectral analysis codes, and theoretical models for the transport of energy and particles from the photosphere through the corona and into the solar wind. Recently we have developed a new approach for analyzing solar spectra which yields more reliable determinations for the relative elemental abundances in the corona. We are also carrying out a series of DR and electron impact ionization measurements using TSR so that we can generate more accurate ionization balance calculations of the corona and thereby better spectral models.

Last updated: 30 June 2008.