Molecular Spectroscopy Symposium June 2013 Identification and Assignment of the First Excited Torsional State of CH 2 DOH Within the o 2, e 2 and o 3 Torsional Levels John C. PEARSON, Shanshan YU Jet Propulsion Laboratory, California Institute of Technology Laurent H. COUDERT LISA, CNRS/Universités Paris Est et Paris Diderot L. MARGULÈS, R.A. MOTIYENKO Laboratoire PhLAM, Université des Sciences et Technologies de Lille S. KLEE, Physikalisch-Chemisches Institut, Justus-Liebig-Universität

2 Molecular Spectroscopy Symposium June 2013 Motivation Theory of Asymmetric-Top Asymmetric-Frame internal rotation is in its infancy –Three ground state examples HCOOCH 2 D, CH 3 CH 2 OH, CH 2 DOH all that exists –CH 2 DOH has large effects and a comprehensive IR and MW data set CH 2 DOH was first discovered in the ISM by Jacq et al., 1993, A&A 271, 276 CH 3 OH is often optically pumped (Far infrared thermal dust emission pumps the torsional bands) –CH 2 DOH should also be similarly excited Issues remain in the abundance of CH 2 DOH relative to CH 3 OD –CH 2 DOH is greatly enriched after cold processing –CH 3 OD is equally abundant to CH 2 DOH in Orion KL!  Quasi-liquid phase on evaporating grains???  Something we don’t know (i.e. partitioning wrong due to pumping?)

3 Molecular Spectroscopy Symposium June 2013 C s symmetry; All wave functions are even (A’ or e) or odd (A” or o) Torsion characterized by number of nodes; Ground state e 0, e 1 and o 1, v t =1 o 2, e 2 and o 3 e to e a-type or b-type o to o a-type or b-type e to o c-type or x-type ( x is  K a =even &  K c =even) o to e c-type or x-type ( x is  K a =even &  K c =even) All are observed; e 0 -e 1 a-types are weak and the x-types generally require mixing OC H H H D Symmetry and Selection Rules

4 Molecular Spectroscopy Symposium June 2013 Spectroscopy Last year we reported the ground state (Pearson, Yu & Drouin, J. Mol. Spectrosc. 280, 119 (2012). –Term values to e 0 K a =10, e 1 K a =9 and o 1 K a =9 determined – a R branches to K a =11 identified for all states –Nearly complete spectrum GHz Last year we also reported identification and assignment of 76 torsional sub- bands (El Hilali, Coudert, Konov, & Klee, J. Chem. Phys. 135, (2011). –Complete Far-IR cm -1 spectrum The combination of calculated band origins, some assigned Q-branches, and microwave accuracy ground state term values provided a basis for assignments –Torsion effects much large in excited states so THz spectra needed

5 Molecular Spectroscopy Symposium June 2013 New Data Microwave Spectra recorded in , , , & GHz regions at JPL & Lots of unassigned lines in previous data o 1 K=11 to e 1 K=10 Q

6 Molecular Spectroscopy Symposium June 2013 Assignments Boot-strap assignments of ground state –Identified Q-branches connecting ground state to e 0 K=14, e 1 K=13 and o 1 K=13 –Confirmed previous a R-branch assignments –Identified a R-branches to e 0 K=14, e 1 K=13 and o 1 K=13 –Checked assignments with multiple loops from other Q branches  6 Q branches are possible for each K a value in each state –Only issue identified is weak perturbation in e 1 J=20 Fit all the new bands with power series model –B*J(J+1)-D*[J(J+1)] 2 +H*[J(J+1)] 4 +…. –e 1 K=12 fit with 4 J’s weighted out Unidentified strong lines are excited torsional states! –Many Q-branches were easily located –P/R branches on series of very strong lines

7 Molecular Spectroscopy Symposium June 2013 Ground-State Torsional Structure There is a real difference in e 1 /o 1 relative to e 0 (B+C)/2 is significantly smaller in e 1 /o 1 A is slightly smaller in e 1 /o 1

8 Molecular Spectroscopy Symposium June 2013 Microwave Assigned Band K=0 K=1 K=2 K=3 K=4 K=5 K=6 K=7 K=8 K=9 o2 e2 o aR branch assigned and confirmed aR branch assignment only not assigned P, Q and/or R in spectrum Number is calculated Q origin Branch confirmed with loops

9 Molecular Spectroscopy Symposium June 2013 IR Bands Assigned K=0 K=1 K=2 K=3 K=4 K=5 K=6 K=7 K=8 K=9 o2 e2 o3 e0 e1 o1

10 Molecular Spectroscopy Symposium June 2013 v t =1 Structure Internal rotation is still hindered especially in o 2, but becomes nearly free rotor thereafter

11 Molecular Spectroscopy Symposium June 2013 Interaction of o 2 K=0 and K=2 o 2 K a =2 K c =J-1 o 2 K a =0 or 2, K c =J or J-2 o 2 K=1 e 2 K=0 K a =0, K c =J is completely mixed with K a =2 K c =J-2 due to asymmetry Extra bands are observed in all cases, asymmetry splitting is enormous

12 Molecular Spectroscopy Symposium June 2013 The 4-state interaction o 3 K=3, o 3 K=2, e 2 K=4 & o 3 K=1 K=2 of o 3 remains unconnected. It will reside between e 2 K=4 and o 3 K=3. There will be a D ab interaction with o 3 K=3. No crossing to J=23

13 Molecular Spectroscopy Symposium June 2013 e 2 K=8 and e 1 K=12 Interaction has x-symmetry (  K a =4,  K c =4) and is very weak (d 1 = (59) x10 -4 MHz fits the data) Probably only allowed due to mixing {i.e. a-type Coriolis between o 1 and e 1 (0,1) and a-type Coriolis between e 2 and o 1 (4,3/5)}

14 Molecular Spectroscopy Symposium June 2013 Future Work Finish IR assignments connecting e 0, e 1, o 1, o 2, e 2, and o 3 Connect o 3 K=2 to the rest of the levels (3 possible bands) –More will be allowed by mixing Assign higher K a values in o 2, e 2 and o 3 Add IR bands involving e 3, e 4 and o 4 –Identify a R-branches confirming assignments with loops –Identify microwave P,Q, & R branch connections –Understand why o 3 K=8 is asymmetry Add IR bands involving o 5, e 5, o 6 and e 6 –Identify a R-branches confirming assignments with loops Assign the rest of the IR spectrum

15 Molecular Spectroscopy Symposium June 2013 Acknowledgements Support for part of this work, part of the NASA Herschel Science Center Theoretical Research/Laboratory Astrophysics Program, was provided by NASA through a contract issued by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA." Part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration