1. H. S. P. Müller, N. Wehres, O. H. Wilkins, F. Lewen, S. Schlemmer,
Spectroscopic Study and Astronomical Detection of Vibrationally Excited n-Propyl Cyanide
H. S. P. Müller, N. Wehres, O. H. Wilkins, F. Lewen, S. Schlemmer,
A. Walters, R. Vicente, D. Liu, R. T. Garrod, A. Belloche, K. M. Menten
Olivia: predoctoral Fulbright
71st ISMS, Urbana-Champaign, IL, 20 – 24 June 2016, WH01

2. Motivation  Can we see lines of vibrationally excited n-PrCN ?
n-Propyl cyanide (n-C3H7CN) detected toward Sagittarius B2(N),
A. Belloche et al., A&A 499 (2009) 215–232,
in a line survey at 3 mm using the IRAM 30 m radio telescope,
A. Belloche et al., A&A 559 (2013) A47
ALMA Cycles 0/1 survey at 3 mm toward Sgr B2(N),
A. Belloche et al., A&A 587 (2016) A91,
n-PrCN seen with very high S/N toward Sgr B2(N2)
A. Belloche et al., Science 345 (2014) 1584–1587
 Can we see lines of vibrationally excited n-PrCN ?

3. What do we know about n-PrCN ?
2 conformers, anti and gauche
E. Hirota, J. Chem. Phys. 37 (1962) 2918
MW, v = 0 (with lines) and A, B, C for 4 lowest vib. states each
K.Vormann & H. Dreizler, Z. Naturforsch. 43A (1988) 338
(J. Demaison & H. Dreizler, Z. Naturforsch. 37A (1982) 199)
FTMW, eQq, internal rotation, parameters
G. Wlodarczak et al., J. Mol. Spectrosc. 127 (1988) 178
mmW, , parameters
J. R. Durig et al., Phys. Chem. Chem. Phys. 3 (2001) 766
IR (gas phase > 300 cm–1), Raman, E
A. Belloche et al., Astron. Astrophys. 499 (2009) 215
parameters

4. Some numbers on n-PrCN B0: 2268 3268 MHz C0: 2153 2705 MHz
anti is higher than gauche (by 40 ± 3 cm–1)
A0: MHz
B0: MHz
C0: MHz
: – –0.8471
a: D
b: D
c: ~0.45 D

5. Low-lying Vibrational States of n-PrCN
400
300
200
100
303
302
291301
281301
271
301
291
281
261
171
181
181301
Evib/cm–1
thick lines: v = 0 plus states which are subject of this presentation

6. Recorded Spectra ~36 – 70 GHz:
7 m double path cell, ~1 Pa, synthesizer, diode detector
~89.6 – GHz:
7 m double path cell, ~1 Pa, synthesizer + multiplier, diode detector
(310.0 – GHz:
4 m double path cell, ~1 Pa, synthesizer + multiplier, diode detector)

7. 14N Quadrupole Splitting in gauche-n-PrCN
J, Ka = 7, 6 – 6, 6
J, Ka, Kc = 13, 1, 12 – 13, 0, 13
intensity drops with excitation of v30; harder to see: chi_aa changes slightly

8. a-Type R-branch Transitions of anti-n-PrCN
 v30 = 1 o v18 = 1
Ka > 2 occur in a narrow frequency window for anti – at least below 127 GHz.

9. Interactions between v18 = 1 and v30 = 2 of a-n-PrCN
E/cm–1
500
650
350
200 10 14 20 22 23 13
v18 = 1
v30 = 2
v18 = 1: deviations at higher Ka
largest at Ka = 14: –1.63 to –2.95 MHz
(J" = 20 – 27)
v30 = 2: deviations at higher Ka
largest at Ka = 13: to MHz
(J" = 20 – 27; tent. Ka = 14 wrong)
 rotational (Coriolis-type) resonance
Fermi resonance at Ka = 22/23
E = (20) cm–1
F = (15) cm–1
Gc = (16) MHz

10. Overview of Results gauche, v30 = 1 & 2, v29 = 1:
a-type R-branch: J  23, Ka  20
a-type Q-branch (Ka = 0, 2): J  61, Ka  11
b-type: J  65, Ka  11
gauche, v28 = 1:
a-type R-branch: J  22, Ka  18; several broad, some split
b-type R-branch: J  22, Ka = 1  0, 2  1; J  10, Ka = 5 – 4 ??
anti, v30 = 1 & 2, v18 = 1
a-type R-branch: J  29, Ka  24
b-type: J  48, Ka = 1  0
anti, v29 = 1:
a-type R-branch: J  29, Ka  18
b-type: J  34, Ka = 1  0 ?? (2 tentative sets of 6)

11. The Star-forming Region Sagittarius B2
most massive star-forming region
in our Galaxy (~ 107 M)
~100 pc from Galactic Center
2 massive clumps, (M) and (N),
hosting clusters of UC HII regions
Central Molecular Zone at 870 µm
ATLASGAL/LABOCA & Planck; © MPIfR/A. Weiß
Sgr B2(N)
Sgr B2(N) at 850 µm (SMA; Qin et al., 2011)
2 hot cores: N1 (or LMH) & N2
different vlsr (10 km/s); 5" apart (0.2 pc)
many COMs first detected there
very high column densities (> 1025 cm–2)
key for detection of COMs

12. Exploring Molecular Complexity with ALMA
3 mm spectral line survey of Sgr B2(N) in Cycles 0 and 1 (84.0 – GHz)
angular resolution: 1.6" (median)
~ 12 % der Linien > 3 K sind U; zu vermuten: hauptsächlich höhere Zustände von EtCN und VyCN.
sensitivity to compact emission: factor ~20 compared to our IRAM 30 m survey
status: analysis ongoing; published: detection of i-PrCN (Science, 2014);
deuterated COMs, ROH & RSH, C2H5CN with 2 13C (all A&A, 2016)

13. Vibrational States of a-n-PrCN toward Sgr B2(N2)
was Du sagen könntest, ist, dass das LTE Modell für die angeregten Zustände die selben Parameter als für den Grundzustand hat,
i.e. LTE ist in dieser Quelle für dieses Molekül eine sehr gute Annahme. Das macht die Detektion von v > 0 sehr sicher.
gauche ähnlich ...

14. Conclusion and Outlook
Lowest 4 vibrational of states of each n-PrCN conformer studied up to 127 GHz
Extend study to 500 GHz (advanced for v = 0)
Extend study to higher excited vibrational states
Lowest 4 vib. states identified in early ALMA data (highest ones on the edge)
Higher states may be observable in more sensitive ALMA data