1. THE MICROWAVE SPECTROSCOPY OF AMINOACETONITRILE IN THE VIBRATIONAL EXCITED STATES 2
(Toho Univ.a, Univ. Toyamab)
Chiho Fujitaa, Haruka Higurashia, Hiroyuki Ozekia, and Kaori Kobayashib
2016 Jun 21st
International Symposium on Molecular Spectroscopy, Illinois

2. Road to Glycine Glycine Gas Phase Rxn. Dust Surface Rxn. Strecker Rxn.
CH3NH2
Gas Phase Rxn.
Dust Surface Rxn.
Strecker Rxn.
Gas-Dust Rxn.
Others

3. Motivation: Origin of Life
Search for Glycine in Interstellar cloud
Amino acid
Glycine (NH2CH2COOH)
Alanine, Glutamine, etc…
Life
Protein
Example of Previous Attempts to Search for Glycine
Freq.(GHz)
Sources
Detected ?
Brown et al. (1979)
Sgr B2, Ori A, etc. ×
Hollis et al. (1980)
Sgr B2
Combes et al. (1996)
Sgr B2, Orion
Ceccarelli et al. (2000)
101, 216
IRAS
Kuan et al. （2003）
Sgr B2, Ori KL, W51 e1/e2 ？
Etc.
I’d like to introduce origin of life, amino acid shortly.
Our life is consist of protein, similarly protein consists of amino acid.
So usually glycine has been used to explore amino acid in interstellar regions.
This table is example of previous search for glycine.
Until Kuan et al. (2003) there were no reports to detect glycine.

4. Synthesis of amino acid via Strecker Reaction
Strecker Syntheses (Strecker (1850))
One of the famous reactions that produce amino acid
in laboratory.
H2O
Methaneimine
CH2NH
Aminoacetonitrile
NH2CH2CN
Glycine
NH2CH2COOH
HCN
H2CO
NH3 +
In this study, we focused this generating pathway, Strecker reaction.
This is the one of the famous reaction that produce amino acid in the lab frame.
In this reaction, AAN is the precursor of glycine.

5. Structure of AAN AAN NC 1.4760Å CC’ 1.4611Å C’N’ 1.1594Å CH 1.0940Å NH
1.0138Å
NCC’
114.54°
HCH
102.4°
HNC
109.6°
HNH
107.3°
CC’N’
180.0°
Hydrogen
Carbon
Nitrogen N N’ C C’
This is the structure of AAN.
Pickett (1973)

6. Previous Pure Rotational Studies of AAN in the Ground State
MacDonald & Tyler
1972
Measured AAN spectra in the microwave region.
a-type: 3 lines b-type: 2 lines
Pickett
1973
Measured AAN and its deuterated isotopologues
(NHD-, ND2-) spectra in microwave region.
Determined electric dipole moment.
　　　　　μa =2.577(7)D, μb =0.5754(10)D
Brown et al.
1977
Determined hyper fine coupling constant
of nitrogen nuclei.
Bogey et al.
1990
Measured AAN spectra in the millimeter wave region.
　　J’ ≤ 40 a-type: 110 lines, b-type: 5 lines.
Belloche et al.
2008
Reanalysis of the previous data.
Motoki et al.
2013
Extension to the Terahertz region.
Corrected assignment of the b-type transitions
J’ ≤ 40 a-type: 110 lines, b-type: 5 lines.
This table is previous studies of AAN.
First, MacDonald & Tyler measured AAN spectra in microwave region.
Next, Pickett measured AAN and its deuterated isotopologues (NHD-, ND2-) spectra in microwave region,
and decided electric dipole moment. μa =2.577(7)D, μb =0.5754(10)D.
Dipole of a-axis is about five times larger than that of b-axis.
Next, Brown et al. determined hyper fine coupling constant of Nitrogen nuclei.
Green letter is amino nitrogen’s hyper fine coupling constant.
Blue letter is nitrile nitrogen’s one.
The last, Bogey et al. measured AAN spectra in millimeter wave region, and determined molecule constant.

7. Detection of AAN towards Sgr B2(N)
Belloche et al. (2008) succeeded to detect
AAN’s millimeter wave spectra towards Sgr B2(N)!!
Detected region ~260GHz
Detected line a-type transitions
GHz
After that, with this revised molecular constant, Belloche et al. (2008) succeeded to detect AAN’s millimeter wave spectra towards Sgr B2(N)!!
This figure is example of detected line.
The vertical axis is main beam temperature, horizontal axis is frequency.
The red line is shows AAN’s spectra line.
CDMS

8. Low-lying Vibrational Excited States
Observed Frequency (cm-1) a
Ab Initio Frequency (cm-1) b
Mode Description
558
563
NCC bending
370
379
NH2-CH2 torsion
247
265
NH2 torsion
235
208
CCN bending
According to the CDMS catalog, b-type of AAN predicted lines have had large error in millimeter and sub-millimeter wave region.
Because b-type transitions have not been measured well, and HK ,h1～h3, and higher constants have not determined well.
So in this study, we measured pure rotational spectra from millimeter to sub-millimeter region
to improve AAN molecule constant to measure mostly b-type and higher Ka’ transition.
B. Bak, E. L. Hansen, F. M. Nicolaisen, O. F. Nielsen, Can. J. Phys., 53, 2183 (1975).
G. M. Chaban, J. Phys. Chem. A 2004, 108,
It is quite likely to observe pure rotational spectra in these vibrational excited states.
They would be useful for astronomical identification.

9. in the Vibrational Excited States
Rotational spectra
in the Vibrational Excited States
Last year we reported several vibrational excited states.
Extended measurements and assignments.

10. Experiment by Using Frequency-modulated
sub-millimeter wave spectrometer
Measured region:114～450 GHz
Sample pressure:about 8×10-3 Pa.
Glass Cell
Oscilloscope
Filter
PSD
Modulator PC
Frequency
Synthesizer
Rb clock
GPS ×n
Pirani gauge
Diffusion pump
Detector
Amp
Gas
Multiplier
In our experiment, we used Frequency-modulated sub-millimeter wave spectrometer in Toho Univ..
Measured region is 122～188 GHz, 372～537 GHz, and 621～661GHz.

11. Low-lying Vibrational Excited States
Symmetry (approximate)
Observed Frequency (cm-1)a
Force Field Analysis (cm-1) a
Ab Initio Frequency (cm-1) b
Ab Initio Frequency (cm-1) c
Mode Description
In-plane
558
595
563
543.4
NCCN bending
Out-of plane
370
361
379
377.2
CC≡N bending
247
222
265
259.6
NH2 torsion
216
261
208
204.9
According to the CDMS catalog, b-type of AAN predicted lines have had large error in millimeter and sub-millimeter wave region.
Because b-type transitions have not been measured well, and HK ,h1～h3, and higher constants have not determined well.
So in this study, we measured pure rotational spectra from millimeter to sub-millimeter region
to improve AAN molecule constant to measure mostly b-type and higher Ka’ transition.
B. Bak, E. L. Hansen, F. M. Nicolaisen, O. F. Nielsen, Can. J. Phys., 53, 2183 (1975).
G. M. Chaban, J. Phys. Chem. A 2004, 108,
M. P. Bernstein, C. W. Bauschlicher Jr., S. A. Sandford, Advances in Space Research 33 (2004) 40–43

12. Vibrational Excited States Observed Frequency (cm-1)
V0: ground state
V1: 235 cm-1
V2: second excited state of V1
V3: 247 cm-1
V4:
V5: 270 cm-1
V6: 270 cm-1
Observed Frequency (cm-1)
Relative intensity
Mode Description
558
0.06
NCC bending
370
0.16
NH2-CH2 torsion
247
0.29
NH2 torsion
235
0.31
CCN bending
This is example of b-type transitions.
We have been able to measure higher Ka lines like that.

13. Molecular Constants (up to 4th order)
(MHz)
Ground statea V1 V3 V5 V2 V4 V6 A
(102)b
(221)
(247)
(235)
(173)
(47)
(75) B
(139)
(69)
(68)
(56)
(109)
(270)
(33) C
(139)
(72)
(53)
(36)
(85)
(240)
(237)
DJ×103
(108)
(132)
(85)
(51)
(41)
(267)
3.1559(77)
DJK×103
(138)
(127)
(220)
(109)
(227)
(239)
(76)
DK×103
(78)
544.55(280)
854.44(315)
693.71(307)
305.2(86)
523.(117)
23.(305)
d1×103
(41)
(209)
(270)
(252)
(45)
(176)
(32)
d2×103
(96)
(63)
(123)
(95)
(40)
(160)
0.0371(34)
Relative
Intensity
1.00
0.34
0.31
0.17
0.13
0.11
0.06
Vib. Modec
n18
n17
n16
2n18
n17 +n18
n16 +n18
ΔE (cm-1)
235
247
370
～470
～480?
～605?
# of a-type
232
314
258
226
313
106 64
# of b-type
264 85 47 5 J’
1-74
13-57
12-46
10-50
10-51
13-22
9-19
Ka’
0-23
0-12
0-11
0-10
0-9
0-5

14. Summary and Future Plan Thank you for your ATTENTION !!
Rotational spectra in 6 vibrational excited levels were assigned and analyzed based on intensity and rotational constants.
A few MHz to 10 MHz deviations from the model at high J, K were noted in the analysis.
Analysis including the interaction betweeen the vibrational states are planned.
This study was supported by KAKENHI.
Funding
Thank you for your ATTENTION !!