Terahertz spectroscopy of deuterated methylene bi-radicals, CHD and CD 2 Stéphane Bailleux June 25, 2015 – 70 th ISMS Meeting

Contributor Toho University (THz) H. Ozeki acknowledgements Measurements

Motivation Chemistry the parent carbene smallest polyatomic with triplet ground state key role in many chemical systems (astrochemistry) Spectroscopic challenges Theoretically light & floppy (breakdown of Watson Hamiltonian) difficult to treat quantum chemically and to predict levels Experimentally Highly reactive (towards hydrocarbons) most lines are in the THz or far-IR frequency regions

CH 2, a key interstellar species Identified in hot cores in dense interstellar clouds A key intermediate in interstellar carbon chemistry C + + H 2  CH hν CH H 2  CH H CH e -  CH 2 + H deuterium fractionation: CH HD  CH 2 D + + H 2 CH 2 D + + e -  CHD + H or : CH 2 + D CHD e -  CHD + D or : CD 2 + H detection in Orion IRc2 ? Roueff et al. JPCA (2013)

Hi-resolution rotational spectroscopy Far IR Laser Magnetic Resonance CH 2 ( 3 B 1 ) : 1982 CHD ( 3 A ʺ ) : 1994 CD 2 ( 3 B 1 ) : 1983 Microwave / Millimeter-wave isotopologue Number of pure rotational transitions f Max (THz) CH CD CHD0

Millimeter-wave spectroscopy of CHD FIR – LMR observations our work Triplet ground state: |S| = 1 H SS =  f (3 S a ² –S²) + β (S b ² –S c ²)

Observation

parameterCH 2 CHD MHzglobal analysisour workFIR-LMR rotation A (447) B (3) (21) C (32) (21) Δ K (498) Δ NK (3) Δ N δ N δ K Φ K Φ NK Φ KN fine structure aa (25)  (75) (75) (ε ab +ε ba )/ ε aa (18) ε bb (50) ε cc Preliminary results (A&A 527, A64, 2011): more transitions planed to be measured: 1 11 ← 0 00 : ~1773 GHz 1 11 ← 2 02 : ~821 GHz

CD 2 at THz frequency region (Toho Uni.) H. Ozeki (Toho Univ.) Production Pyrolysis (800 K / 1000 °F) of (CD 3 CO) 2 O (acetic anhydride-d 6 ) to produce CD 2 CO Mild discharge of CD 2 CO with Ar Low yield

Example of spectrum 6 15 – 6 06, F3 : MHz

Example of spectrum 2 12 – 1 01, F2 : MHz

CD 2 at THz frequency region Current progress on measurements : 1 11 – 0 00 at 1.224, 1.228, THz (Astronomically relevant) Current progress on measurements : 1 11 – 0 00 at 1.224, 1.228, THz (Astronomically relevant) 7 16 – 7 07 at 1240 GHz 8 17 – 8 08 at 1316 GHz 9 09 – 8 18 at 1351 GHz The 3 fine-structure components have been observed for each 5

CH 2 CD 2 global analysisour work rotation A (33) 000 B (95) 0 C (33) 0 Δ K (FIR-LMR) Δ NK (32) Δ N (39) δ N (10) δ K (FIR-LMR) Φ K (FIR-LMR) Φ NK (10) Φ KN (FIR-LMR) fine structure  (2)0  (26) ε aa (29) ε bb (73) ε cc (13) Parameters (MHz)

Concluding remarks Significant extension of number of lines measured (CD 2 ) 33 distinct transition frequencies (x 2) rms = 77 kHz More lines should be measured  those astronomically relevant low N  hyperfine-structure pattern (weak lines) but hyperfine parameters not known (CD 2 )  more efficient method of production required (CD 2 ) discharge in CD 4 samples (expensive) Paper in preparation

Announcement Post-Doctoral Position Available at the University of Lille 1 year, starting from 01/2016 Net income : 2000 € Topic: spectroscopic detection of astronomically relevant species from the mmw to the THz frequency region Contact:

Example of spectrum

Millimeter-wave spectrometer (Toho) Precursor (CD 3 CO) 2 O

N2N2 to pump LN 2 solenoid head pressure gauge parabolic mirror gas inlet anode cw power supply 5 kV / 600 mA BWO power suppl y 320 MHz  10 MHz PLL Feedback   IF GHz local oscillator ~10 MHz Ref. oscillator 10 MHz Rb atomic clock Phase Sensitive Detector InSb Digital Oscilloscope phase modulation BWO pre- amplifier LN 2 -cooled absorption cell ballast Spectrometer (Lille Univ.)