! File: 1066C.PROP ! Database: PEPDB ! Date: 16-FEB-1994:00:25:03 coverpage: title_1: CARBON CHEMISTRY IN INTERSTELLAR DIFFUSE CLOUDS - THE C2 MOLECULE title_2: :CYCLE 1 OBSERVATIONS sci_cat: INTERSTELLAR MEDIUM proposal_for: GTO/OS cont_id: 1066 pi_title: PROF. pi_fname: DAVID pi_mi: L. pi_lname: LAMBERT pi_inst: TEXAS, UNIVERSITY OF pi_country: USA pi_phone: 512-471-7438 keywords_1: INTERSTELLAR MOLECULES - C2 - MOLECULAR PROCESSES - keywords_2: CHEMISTRY OF C2 hours_pri: 4.00 num_pri: 11 hrs: X pi_position: PROFESSOR ! end of coverpage abstract: line_1: Observations of the C2 molecule in interstellar diffuse clouds are based on the line_2: Phillips near-infrared system. The ultraviolet D-X (lambda ~2310 A) and F-X line_3: (lambda ~1341 A) transitions should provide detectable C2 lines on HRS echelle line_4: spectra for lines-of-sight for which Phillips system lines are essentially line_5: undetectable. line_7: Observations of C2 will be attempted for line of sight containing rather little line_8: H2 (log N(H2) <~ 20.6). The D-X and F-X bands transitions will be calibrated line_9: against the Phillips system through observations of zeta Oph. line_11: The relation between C2, H2, and other abundant molecules will be interpreted line_12: using cloud models and thorough chemical reaction networks. Rotational line_13: excitation will also be measured and interpreted. ! ! end of abstract general_form_proposers: lname: LAMBERT fname: DAVID mi: L. inst: TEXAS, UNIVERSITY OF country: USA ! lname: DANKS fname: ANTHONY mi: C. inst: GODDARD SPACEFLIGHT CENTER country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: High S/N HRS echelle spectra of bright slightly reddened stars at 1341 A line_2: (ECH-A) and 2313 A (ECH-B). Total exposure has been broken down into four line_3: chunks. Smaller intervals are assumed here in order to reduce fluctuations line_4: from photocathode granularity. Detailed procedure TBD following SV and full line_5: testing of HRS. line_7: Exposures of priority 1 may be scheduled in cycles 2 and 3. Others may be line_8: observed as convenient. ! question: 4 section: 1 line_1: As explained in 2, interstellar C2 along slightly reddened lines of sight is line_2: detectable in the ultraviolet but not the optical. ! question: 6 section: 1 line_1: This program calls for high S/N spectra. I request that it not be scheduled line_2: until pertinent calibration data for HRS obtained in SV tests have been line_3: digested by the STScI. Based on my experience with ground-based detectors, I line_4: suspect that a bright star will have to be observed in order to achieve an line_5: adequate calibration of the pixel-pixel variations: flat-fielding using a line_6: monochromatic lamp is unlikely to yield adequate accuracy. In the event that line_7: observation of a star is necessary, the observing time may be taken from that line_8: assigned to low priority stars. Note too that special techniques may be line_9: necessary to ensure high S/N: e.g., positioning the oine on the optimum line_10: portion of the photocathode. It seems impossible to describe their requests line_11: now. ! question: 7 section: 1 line_1: Spectra as reduced by standard STScI software will be analyzed at the line_2: University of Texas. Synthetic profiles of the C2 bands will be fitted to the line_3: observations to yield the C2 column density, rotational temperature, the radial line_4: velocity, and the intrinsic line profile. line_6: Models of the clouds and the carbon chemistry will be used to fit the C2 and line_7: other molecular data (e.g., CO, CH, CN). ! question: 8 section: 1 line_1: None. Adequate data on optical atomic and molecular line exists. ! question: 10 section: 1 line_1: University and Departmental computing facilities. ! question: 13 section: 1 line_1: HRS echelle spectra will provide column densities for the C2 molecule along line_2: lines of sight with relatively little molecular H2 (log N(H2)