How can synchrotron-based FTIR spectroscopy contribute to astrophysical and atmospheric data needs? A.R.W. McKellar National Research Council of Canada, Ottawa

Herschel Space Telescope James Webb Space Telescope ALMA Atacama Large Millimeter Array SOFIA Stratospheric Observatory For Infrared Astronomy ACE Atmospheric Chemistry Experiment ENVISAT MetOp OCO (non) Orbiting Carbon Observatory Terahertz Remote Sensing Billions of $ invested worldwide in THz and IR astronomical and atmospheric missions. In many cases, the required laboratory data are unavailable, insufficient, or unreliable. Can synchrotron FTIR help to address this problem?

Synchrotron-based IR spectroscopy For some IR applications, SR offers no advantage But for high spatial resolution (condensed-phase studies), or very high spectral resolution (gas-phase studies) the brightness of SR is ideal Here, SR gives us 5 to 25 times more signal through a 2 mm aperture than a conventional source. This promises up to 600 times faster data acquisition.

Synchrotron-based IR spectroscopy The synchrotron is simply providing a bright continuum source (like a very expensive globar) High spectral resolution IR is new for synchrotrons – pioneered at MAXLab and LURE New user facilities for high-res (gas-phase) IR spectroscopy are now starting up at CLS, SOLEIL, and the Australian and Swiss Synchrotrons Synchrotron advantage is presently limited by noise – mechanical vibrations of the beamline mirrors

High resolution synchrotron IR spectroscopy was pioneered by Bengt Nelander at MAXLab in Lund, Sweden These photos are from 2004

FIR Beamline AILES at Synchrotron SOLEIL near Paris Pascal Roy Olivier Pirali

The Australian Synchrotron Monash University, near Melbourne

Swiss Light Source Paul Scherrer Institute, Villigen (between Zurich and Basel)

Singapore Synchrotron Light Source ISMI infrared beamline

Canadian Light Source September, 2008

January, 2009

CLS Parameters Energy: 2.9 GeV Current: 200 mA Circumference: 171 m 12 straight sections, 5.2 m long RF: 500 MHz, 2.4 MV, supercon Injection: 250 MeV LINAC full energy booster ring Main building: ~ 85 x 85 m

Bruker IFS 125 HR spectrometer: max optical path difference = 9.4 m instrumental resolution ~ cm-1 (18 MHz)

0.3 m gas cell absorption paths up to 12 m 2 m gas cell absorption paths up to 80 m coolable to ~80 K

Synchrotron-based IR spectroscopy With continuing improvements, SR now has a significant advantage from 100 ~ 800 cm -1 at CLS But we are aiming for better performance Reduce noise at source: better isolation of offending cooling pumps, heat exchangers, pipe runs, etc. Reduce noise at beamline: more isolation, better mounting of beamline mirrors Active optics to stabilize the input radiation on the spectrometer aperture

Acrolein CH 2 CHCHO (propenal) fundamental 8-atom species planar near-prolate asymmetric rotor interstellar molecule combustion byproduct (forest fires) potent respiratory irritant (cigarette smoke, smog) low lying vibrational states of acrolein

17 band of acrolein, CH 2 CHCHO K a = 7 – 6 Q-branch nominal resolution cm -1

Acrolein 18 central region

With cm -1 line width and reasonable signal-to- noise ratio, positions can be measured to << cm -1 (for unblended lines). Half of the acrolein lines here are measured to cm -1 (1 MHz !!) or better.

Pyrrole (c-C 4 H 4 NH) 16 band D.W. Tokaryk & J. Van Wijngaarden (2008)

Azetidine (C 3 H 6 NH), 16 band Jennifer van Wijngaarden, University of Manitoba

q Q[(2,5)-(0,4)E] q Q[(3,-10)-(1,-9)E] q R[(2,14)-(0,13)E] Methanol (CH 3 OH) - new high torsional assignments L.-H. Xu, R.M. Lees, University of New Brunswick (v t, K)

CDF 3 4 / band system A. Predoi-Cross, Lethbridge P. Pracna, Prague A. Ceausu-Velcescu, Perpignan B. Billinghurst, CLS

CH 3 COD * 200 K * 48 m path L.H. Coudert, LISA Université Paris 12

Cl 2 CS (thiophosgene) 40 m path * 0.02 Torr

~1800 transitions fitted with rms deviation of cm -1 (2 MHz)

How can synchrotron-based FTIR spectroscopy contribute to astrophysical and atmospheric data needs? Compared to conventional IR sources, synchrotrons promise a combination of –Higher spectral resolution –Higher signal-to-noise ratio –Shorter observation time –Better matching to absorbing molecules (e.g. supersonic jet) But as observation time becomes shorter we become limited by –Time for sample preparation and change (e.g. in a large cooled gas cell) –Time for data analysis!!

Coherent Synchrotron Radiation

tends to be noisy because of its nonlinear nature and the presence of beam instabilities

Science Goals Complexes & Clusters Important intermolecular vibrations are located in the far IR. Spectroscopy directly measures intermolecular forces, important for fields like molecular collisions, condensation, solvation, and energy transfer; also provides stringent & unambiguous tests for quantum chemistry calculations. Sampling techniques: cooled long-path cell; future supersonic jet. THz Laboratory Astrophysics: Ions & Radicals Far IR is now being explored by astronomers with new aircraft-, space-, and ground-based observatories. It’s the natural wavelength region for observing ‘cool’ matter in the universe (e.g. stellar and planetary formation). modular 1.5 m gas discharge cell for unstable astrophysical radicals