High Resolution FIR and IR Spectroscopy of Methanol Isotopologues R.M. Lees, Li-Hong Xu Centre for Laser, Atomic and Molecular Sciences (CLAMS) Department of Physics, University of New Brunswick D.R.T. Appadoo, B. Billinghurst Canadian Light Source, University of Saskatchewan

May 14 – Launch of Herschel Space Observatory with HIFI - Heterodyne Instrument for the Far-Infrared Herschel reached L2 Lagrange point in mid-July HIFI was switched off on Aug 3 – anomaly!

Herschel PACS View of Galaxy M51 – June 14

Background and Motivation  The Herschel Space Observatory with the HIFI THz spectrometer on board was launched on May 14 and ALMA is coming – extensive methanol astronomical spectra are imminent and new lab data and insights are needed for all of the isotopic species of this principal "interstellar weed" to construct extensive databases and permit reliable modelling for astrophysical conditions.  The large-amplitude internal rotation in CH 3 OH makes the torsion- vibration energy manifold both complex and interesting, with strong torsion-mediated interactions coupling the different vibrational modes and several unassigned families of substates.  By looking at the isotopologues in detail, we hope for a new VISTA into the vibrational structure [Vibrational Isotopic Shift Technique for Assignment] with further clues to the vibrational identification.

Methanol 1-D Large-Amplitude Torsion O H H H 13 C H K values E tor = F + V 3 /2 V3V3 12 =1 12 =0 0E 0A 12 =2 The torsional energies follow oscillating curves as a function of rotational quantum number K, with A and E torsional symmetry.

Torsional-K-Rotational Energy Structure for CH 3 OH V 3 = cm -1 A E1E1 E2E2 t = 0 t = 1 t = 2 t = 3 (0,15)/(1,13)/(2,11)A (1,10)/(2,7)A (0,12)/(1,9)E (0,9)/(1,5)A ( t,K)TS Level crossings K Values t Lowest Small Amplitude Vibrations

r Q[(2,5)-(0,4)E] r Q[(3,-10)-(1,-9)E] r R[(2,14)-(0,13)E] (v t, K) p P[(2,2)-(0,3)A-] r R[(2,13)-(1,12)A] r R[(3,11)-(2,10)E] FIR Spectrum of CH 3 OH - New High Torsional Assignments

A A A E 2 FIR Spectrum of CH 3 OH – Loomis-Wood Approach E E E E E 1 ???

Origins of new torsional subbands of CH 3 OH

(Moruzzi et al.) ~ 1.8 THz THz Interstellar Lines are Predicted from FTIR Combination Differences K vt

Description obs / cm -1 A' 1 OH stretch3682  CH asym stretch2999  CH sym stretch CH 3 asym bend CH 3 sym bend OH bend CH 3 in-plane rock CO stretch1034 A" 9 CH asym stretch CH 3 o-o-p bend CH 3 o-o-p rock CH 3 torsion 272 Vibrational modes of methanol Wavenumbers from A. Serrallach, R. Meyer and Hs. H. Gunthard, J. Mol. Spectrosc. 52 (1974) Torsional combination bands

CLS FTIR Spectra of 13 CH 3 OH and CD 3 OH CD 3 OH CO stretch OH bend CD 3 bend CH 3 in-plane rock 13 CH 3 OH CD 3 in-plane rock

P(12) P(13) P(14) P(17)P(16)P(15)P(14)P(13)P(12)P(11)P(10)P(9) v t =1 v t =0 Multiplet Structure in the O-18 CO-Stretch Band (v t,K)=(1,-3)E CH 3 18 OH CO-Stretch

CLS FTIR Spectrum of O-18 Methanol CO Stretch Out-of-plane Rock CH 3 Bends ab sb v t = 1← 0 ri v t = 0← 1 oh "U" Subbands In-plane Rock 3A -8E 4A 7A -5E 6E 3E OH Bend 7A 3A 7E 8A

Loomis-Wood Plot for Line Series Identification OH bend, v t = 0 OH bend, v t = 1 In-plane rock, v t = 1-0 U0 subband

K-Reduced Torsion-Vibration Energy Map K Value K-Reduced Energy (cm -1 ) Connect the Dots???

K Value K-Reduced Energy (cm -1 ) O-18 K-Reduced Torsion-Vibration Energy Map (sensitive to  K = 0 anharmonic perturbations) CO stretch, v t = 0 CO stretch, v t = 1 CO stretch, v t = 2 In-plane rock, v t = 0 In-plane rock, v t = 1 Out-of-plane rock, v t = 0 U0 substates CH 3 asym bend, v t = 0 OH bend, v t = 0 OH bend, v t = 1 U1 substates U2 substates

Level-Crossing Resonances J Value J-Reduced Energy (cm -1 ) CH 3 o-o-p rock CH 3 in-plane rock CO stretch O-18 J-Reduced Rot-Tor-Vib Energy Map (sensitive to level-crossings and J-localized perturbations) O-18 CO Stretch - R.M. Lees, Reba-Jean Murphy, Giovanni Moruzzi, Adriana Predoi-Cross, Li-Hong Xu, D.R.T. Appadoo, B. Billinghurst, R.R.J. Goulding and Saibei Zhao, J. Mol. Spectrosc. 256, (2009).

Summary  New highly excited torsional subbands have been assigned in the FIR spectrum of normal CH 3 OH locating 6 new substates for v t = 2, 9 for v t = 3, and 5 for v t = 4 at high K-values, providing predictions for potential THz astronomical lines from combination differences and important new torsional constraints for future global fitting of the ground vibrational dataset.  Vibrational bands have been recorded for the CO-stretching, CH 3 -rocking, OH-bending and CH 3 -bending modes of 13 CH 3 OH, CH 3 18 OH and CD 3 OH.  The K- and J-reduced energy plots of CH 3 18 OH show complex mixtures of fundamental and torsional combination states with torsion-mediated intermode interactions that perturb the regular subband patterns, plus U substates of as yet unconfirmed vibrational parentage.  Isotopic shifts in subband origins and B-values suggest the U states are torsion-rocking combination states, possibly mixed with the OH-bend.