BEGIN:VCALENDAR VERSION:2.0 METHOD:PUBLISH PRODID:-//Missouri State University/Calendar of Events//EN CALSCALE:GREGORIAN X-WR-TIMEZONE:America/Chicago BEGIN:VTIMEZONE TZID:America/Chicago BEGIN:DAYLIGHT TZOFFSETFROM:-0600 TZOFFSETTO:-0500 DTSTART:20070311T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU TZNAME:CDT END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0500 TZOFFSETTO:-0600 DTSTART:20071104T020000 RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU TZNAME:CST END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:9a2ca532-b22d-4d3a-a12f-385b2c2422b3.233969@calendar.missouristate.edu CREATED:20240123T174408Z LAST-MODIFIED:20240123T174408Z LOCATION:Kemper Hall 204 SUMMARY:PAMS Seminar: "Conformer-specific Desorption in Interstellar Ices Probed by Chirped-pulse mm-Wave Rotational Spectroscopy" by Dr. Bernadett e M. Broderick DESCRIPTION:Dr. Bernadette M. BroderickUniversity of MissouriDepartment of Chemistry\n\n\nAbstract:\n\n\nA new technique developed by our group for the detection of molecules desorbed from an ice surface using broad-band rotational spectroscopy will be presented. The approach permits interrog ation of molecules that have undergone the slow warmup process of tempera ture-programmed desorption (TPD)\, analogous to the warmup phase of icy g rains in the interstellar medium as they approach the central protostar. The detection is conformer- and isomer-specific and quantitative\, as aff orded by chirped-pulse rotational spectroscopy. To achieve this\, we comb ine ice TPD with buffer gas cooling\, followed by detection in the millim eter-wave regime. In this presentation\, the sublimation of n- and ipropa nol\, the former of which may be in five different conformational isomeri c forms\, and which display distinct desorption profiles\, will be descri bed. The limited conformational isomerization and temperature-dependent r elative yields of n-propanol conformers observed show that the desorption is highly conformer-specific. In addition to propanol\, the sublimation of propyl cyanide will also be presented\, where the relative abundances of the anti and gauche conformers following room-temperature gas-phase in jection into a 25 K buffer gas cell are compared to that which is observe d following TPD from an ice surface. The conformer distributions observed in the gas phase from room-temperature injection are then used to determ ine their relative energies\, an important parameter needed to interpret the isomer and conformer abundances derived from astronomical observation s. We find the gauche conformer to be the most stable species by ~97±21 c m-1. We further examine the relative conformer abundances following ice d esorption\, which are distinct from those following the gas-phase introdu ction. The ratios measured off the ice correspond to a conformer temperat ure of ~56 K\, which is much lower than their sublimation temperature of 170 K. X-ALT-DESC;FMTTYPE=text/html:<html><head><title></title></head><body><p><b >Dr. Bernadette M. Broderick</b><br><strong>University of Missouri</stron g><br><strong>Department of Chemistry</strong></p>\n<p>Abstract:</p>\n<p> A new technique developed by our group for the detection of molecules des orbed from an ice surface using broad-band rotational spectroscopy will b e presented. The approach permits interrogation of molecules that have un dergone the slow warmup process of temperature-programmed desorption (TPD )\, analogous to the warmup phase of icy grains in the interstellar mediu m as they approach the central protostar. The detection is conformer- and isomer-specific and quantitative\, as afforded by chirped-pulse rotation al spectroscopy. To achieve this\, we combine ice TPD with buffer gas coo ling\, followed by detection in the millimeter-wave regime. In this prese ntation\, the sublimation of n- and ipropanol\, the former of which may b e in five different conformational isomeric forms\, and which display dis tinct desorption profiles\, will be described. The limited conformational isomerization and temperature-dependent relative yields of n-propanol co nformers observed show that the desorption is highly conformer-specific. In addition to propanol\, the sublimation of propyl cyanide will also be presented\, where the relative abundances of the anti and gauche conforme rs following room-temperature gas-phase injection into a 25 K buffer gas cell are compared to that which is observed following TPD from an ice sur face. The conformer distributions observed in the gas phase from room-tem perature injection are then used to determine their relative energies\, a n important parameter needed to interpret the isomer and conformer abunda nces derived from astronomical observations. We find the gauche conformer to be the most stable species by ~97±21 cm-1. We further examine the rel ative conformer abundances following ice desorption\, which are distinct from those following the gas-phase introduction. The ratios measured off the ice correspond to a conformer temperature of ~56 K\, which is much lo wer than their sublimation temperature of 170 K.</p>\n<p></p></body></htm l> DTSTART;TZID=America/Chicago:20240208T160000 DTEND;TZID=America/Chicago:20240208T170000 SEQUENCE:0 URL:https://physics.missouristate.edu/seminars.htm CATEGORIES:Public,Alumni,Current Students,Faculty,Future Students,Staff END:VEVENT END:VCALENDAR