Peter L. Smith

     office:  60 Garden Street 
	      Room P-243
	      Mail stop 50
              Cambridge, MA  02138

     phones:  617-495-4984 or 496-7534

        fax:  617-495-7455
 
       page:  617-896-1241
  
     e-mail:  plsmith@cfa.harvard.edu 

emergencies:  call 617-495-7289 (Donna Coletti),
                         5-4862 (09:30-14:00 only),
                         5-4865, 5-7377, or 5-7051
              to try to locate me

updated (in part): 16 December, 1996

Research Interests

Space Physics

Peter Smith is a Co-Investigator for the Mission Operations and Data Analysis phase of the Ultraviolet Coronagraph Spectrometer (UVCS) instrument on the ESA/NASA SOHO satellite. He is co-chair of the UVCS Science Working Group on Instrument Calibration and Co-Registration, with a particular interest in the radiometric calibration and detector `flat field' response, and manages the UVCS Data Reduction & Analysis Facility (DRAF) at the CfA.

He is also a member of the Science team for the Ultraviolet Coronal Spectrometer that observed the solar corona from the Spartan 201 satellite that was launched and retrieved by STS-64 and 69. The Spartan UVCS will be launched again in late 1997 on STS-87.

Laboratory Astrophysics

Smith has research interests in two areas of vacuum ultraviolet (VUV), far ultraviolet (FUV), and extreme ultraviolet (EUV) laboratory astrophysics:

This work is in collaboration with W. H. Parkinson and K. Yoshino of the CfA, and colleagues at other institutions.

Bibliography:

Clicking on `Bibliography', above, initiates a search of the ADS abstract service ASTRONOMY database. There are some omissions and false `hits', but most papers are listed.

Additional papers can be found through searches of the ADS Instrumentation database and the ADS Physics and Geophysics database. Beware of false `hits'.

Background

Peter Smith grew up in Vancouver, British Columbia, and was graduated from the University of British Columbia with a B.Sc. (with Honours) in Physics. He received the Ph.D. degree, in Physics, from Caltech in 1972 and, after a year of teaching, came to and stayed at the Center for Astrophysics. There, he is also known as Mr. Donna J. Coletti.

In collaboration with others in the laboratory, he has measured transition probabilities (A-values) of allowed lines of iron group elements; made the first measurements of the A-values of some of the spin-changing, `intersystem' lines used in interstellar-cloud abundance determinations and in line-ratio methods for diagnostics of astrophysical plasmas; and measured absorption cross sections and f-values for lines of molecules seen, or expected to be seen, in the absorption spectra of diffuse and translucent interstellar clouds.

He has published 74 papers in books or refereed journals, mostly on these subjects and on instrumentation for high resolution spectroscopy, for FUV and EUV radiometry, and for spectroscopic and radiometric measurements from spacecraft.

Smith served as Secretary of Commission 14 (Atomic & Molecular Data) of the IAU and as a member of the Organizing Committee for the meetings held in August 1994.

Highlights of Recent Research in Laboratory Astrophysics

last update: December 1995

Intersystem Line f-values

In their studies of atoms and ions of astrophysical interest, Smith and colleagues have measured f-values for intersystem lines in low-Z ions. When reliable oscillator strengths are available, these weak lines are particularly useful for interstellar abundance determinations and for plasma density diagnostic techniques that are used by astronomers. The CfA measurements have motivated reevaluation of a number of calculated values of these parameters.

A. G. Calamai, Smith, and S. D. Bergeson, recently published the first measured lifetimes for the 3s2 3p 2Po - 3s3p2 4P intersystem lines of Si II. Cardelli et al. (ApJ 420, L29, 1993) used spectra obtained with the GHRS on HST to study absorption by interstellar silicon toward zeta Oph. They detected absorption by some of the intersystem lines at ~235 nm and by the resonance multiplet at ~181 nm. Column densities derived from both sets of lines agreed, thus confirming both sets of oscillator strengths and the observational and data analysis techniques. Cardelli et al. point out that, because the f-values for the weaker intersystem lines are now available, these will be useful for column density determinations in regions of high silicon abundance where the resonance lines would be saturated.

Molecular photoabsorption cross sections

Smith and colleagues measure photoabsorption cross sections for molecular rotational lines that have been (or could be) used for searches for and detection of molecules in diffuse and translucent interstellar clouds and for determination of molecular column densities there. In addition, they measure other molecular parameters [line assignments, wavelengths, and widths, as well as predissociation probabilities and continuous absorption cross sections] that are essential for theoretical descriptions of the abundances and excitations of interstellar molecules and for comparison of predictions with observations. Some of these measurements are made on gas cooled to \sim30~K, similar to temperatures in interstellar clouds; no other laboratory is capable of such measurements. Their recent paper, High Resolution f-Value Measurements for A-X Bands of CO with 11 < v' < 14, Smith, G. Stark, Yoshino, and K. Ito resolved some uncertainties in the f-values for some high-v' bands of the A(v')-X(0) bands of CO. Definitive interpretations of a number of observations of interstellar CO with the GHRS were plagued by these uncertainties. Our new measured values support those derived from transition moments calculated at the CfA by Kate Kirby & David Cooper (J.Chem.Phys. 90, 4895 1989) but ignored by astronomers until recently.

Last update August, 1996