- Email: [email protected]
Far-Infrared Laser Stark Spectroscopy of13CD3OD
JOURNAL OF MOLECULAR SPECTROSCOPY ARTICLE NO.
176, 439–441 (1996)
0105
LETTER TO THE EDITOR Far-Infrared Laser Stark Spectroscopy of
13
CD3OD
M. Jackson,* G. R. Sudhakaran,† and E. Gansen† *Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003; and †Department of Physics, University of Wisconsin, La Crosse, Wisconsin 54601 Received November 29, 1995; in revised form February 20, 1996 We report here the first observation of the Q-branch multiplet Jk Å J5 R J4 E2, yt Å 1 for the members J Å 9 to 15 of 13CD3OD. These resonances have been observed between the 337-mm line of the HCN laser and the Stark-shifted frequency spectra. The experimental procedure used in this work has previously been described (1, 2). Laser Stark spectra have been taken in both parallel and perpendicular polarizations up to 60 000 V/cm at room temperature. Figure 1 shows a low-voltage spectrum of 13CD3OD in the parallel polarization. The analysis of the laser Stark spectra has previously been discussed (1, 3 – 5). The assignments were based on predictions of energy levels and Stark coefficients provided by Mukhopadhyay (6). The Stark energy shift, DW, of each level was calculated using the formula
S D
DW Å (A / BM2)12 0 CM1, h
[1]
where A, B, and C are the Stark coefficients for a particular energy level and 1 is the applied electric field. The Stark plate spacing was 0.051508 { 0.00005 cm. For the present analysis, the Stark coefficients were calculated using the available molecular constants and the CD3OD values of the electric dipole moment, ma Å 0.867 D and mb Å 1.439 D, in the ground torsional state (7). The observed Stark voltages for the different M-components of the Q-branch multiplet are given in Table 1. The net Stark shift and zero-field frequency for each member of the multiplet are given in Table 2. Only information from the DM Å 0
FIG. 1. Stark absorption spectrum in the low-voltage region for the Q-branch multiplet Jk Å J5 R J4 E2, yt Å 1 of 13CD3OD in parallel polarization at l Å 337 mm. The Stark cell pressure is 60 mTorr.
439 0022-2852/96 $18.00 Copyright q 1996 by Academic Press, Inc. All rights of reproduction in any form reserved.
AID
JMS 7008
/
6t0a$$$581
04-22-96 11:45:06
mspas
AP: Mol Spec
440
LETTER TO THE EDITOR
TABLE 1 Observed Stark Voltages (in V) of Different M-Components in Parallel Polarization (DM Å 0) for the Q-Branch Multiplet Jk Å J5 R J4 E2, yt Å 1 of 13CD3OD at l Å 337 mm
TABLE 2 Measured Net Stark Shifts and Zero-Field Frequencies (in MHz) for the Q-Branch Multiplet Jk Å J5 R J4 E2, yt Å 1 of 13CD3OD
spectra were used due to the heavy overlapping of individual peaks in the DM Å {1 spectra. Laser detuning experiments were used to show that the transition frequencies of J Å 9, 10, 11, 14, and 15 were below while J Å 12 and 13 were above the laser frequency of 890 760.2 MHz (8). The errors in the net Stark shift (rms deviations of the individual shifts), laser frequency (0.2 MHz), and experimental setup (0.5 MHz) were combined to yield the overall uncertainty in the zero-field frequency. The uncertainties in the Stark coefficients were not considered in the present error analysis. Despite these uncertainties, the 13CD3OD zero-field frequencies determined here should contribute significantly to the improvement of the electric dipole moment components and molecular constants because no other high-resolution far-infrared studies have been reported on this molecule. We observe several absorption lines belonging to additional Q-branch and P- (or R-) branch transitions which have not yet been assigned. More extensive spectra and analysis at other laser lines are being pursued and will be reported. Further analysis of the Q-branch multiplet will provide information on the series expansion coefficients.
ACKNOWLEDGMENT We are grateful to Dr. I. Mukhopadhyay of the Centre for Advanced Technology, Indore, India for providing the energy level predictions and Stark coefficients of 13CD3OD.
Copyright q 1996 by Academic Press, Inc.
AID
JMS 7008
/
6t0a$$$582
04-22-96 11:45:06
mspas
AP: Mol Spec
441
LETTER TO THE EDITOR
REFERENCES 1. L. H. Johnston, R. P. Srivastava, and R. M. Lees, J. Mol. Spectrosc. 84, 1–40 (1980). 2. R. L. Bhattacharjee, L. H. Johnston, G. R. Sudhakaran, and J. C. Sarker, J. Mol. Spectrosc. 138, 38–48 (1989). 3. L. H. Johnston, J. C. Sarker, R. L. Bhattacharjee, and G. R. Sudhakaran, J. Mol. Spectrosc. 123, 501–502 (1987). 4. J. C. Sarker, G. R. Sudhakaran, R. L. Bhattacharjee, L. H. Johnston,
5. 6. 7.
8.
I. Mukhopadhyay, and R. M. Lees, J. Mol. Spectrosc. 147, 243–251 (1991). G. R. Sudhakaran, M. Jackson, R. M. Lees, Li-Hong Xu, and I. Mukhopadhyay, Infrared Phys. 34, 661–665 (1993). I. Mukhopadhyay, private communication. I. Mukhopadhyay, P. K. Gupta, and G. R. Sudhakaran, in ‘‘International Conference on Spectroscopy: Frontiers and Perspectives, Bombay, India, 1996.’’ C. C. Bradley and D. J. E. Knight, Phys. Lett. A 32, 59–60 (1970).
Copyright q 1996 by Academic Press, Inc.
AID
JMS 7008
/
6t0a$$$582
04-22-96 11:45:06
mspas
AP: Mol Spec
176, 439–441 (1996)
0105
LETTER TO THE EDITOR Far-Infrared Laser Stark Spectroscopy of
13
CD3OD
M. Jackson,* G. R. Sudhakaran,† and E. Gansen† *Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003; and †Department of Physics, University of Wisconsin, La Crosse, Wisconsin 54601 Received November 29, 1995; in revised form February 20, 1996 We report here the first observation of the Q-branch multiplet Jk Å J5 R J4 E2, yt Å 1 for the members J Å 9 to 15 of 13CD3OD. These resonances have been observed between the 337-mm line of the HCN laser and the Stark-shifted frequency spectra. The experimental procedure used in this work has previously been described (1, 2). Laser Stark spectra have been taken in both parallel and perpendicular polarizations up to 60 000 V/cm at room temperature. Figure 1 shows a low-voltage spectrum of 13CD3OD in the parallel polarization. The analysis of the laser Stark spectra has previously been discussed (1, 3 – 5). The assignments were based on predictions of energy levels and Stark coefficients provided by Mukhopadhyay (6). The Stark energy shift, DW, of each level was calculated using the formula
S D
DW Å (A / BM2)12 0 CM1, h
[1]
where A, B, and C are the Stark coefficients for a particular energy level and 1 is the applied electric field. The Stark plate spacing was 0.051508 { 0.00005 cm. For the present analysis, the Stark coefficients were calculated using the available molecular constants and the CD3OD values of the electric dipole moment, ma Å 0.867 D and mb Å 1.439 D, in the ground torsional state (7). The observed Stark voltages for the different M-components of the Q-branch multiplet are given in Table 1. The net Stark shift and zero-field frequency for each member of the multiplet are given in Table 2. Only information from the DM Å 0
FIG. 1. Stark absorption spectrum in the low-voltage region for the Q-branch multiplet Jk Å J5 R J4 E2, yt Å 1 of 13CD3OD in parallel polarization at l Å 337 mm. The Stark cell pressure is 60 mTorr.
439 0022-2852/96 $18.00 Copyright q 1996 by Academic Press, Inc. All rights of reproduction in any form reserved.
AID
JMS 7008
/
6t0a$$$581
04-22-96 11:45:06
mspas
AP: Mol Spec
440
LETTER TO THE EDITOR
TABLE 1 Observed Stark Voltages (in V) of Different M-Components in Parallel Polarization (DM Å 0) for the Q-Branch Multiplet Jk Å J5 R J4 E2, yt Å 1 of 13CD3OD at l Å 337 mm
TABLE 2 Measured Net Stark Shifts and Zero-Field Frequencies (in MHz) for the Q-Branch Multiplet Jk Å J5 R J4 E2, yt Å 1 of 13CD3OD
spectra were used due to the heavy overlapping of individual peaks in the DM Å {1 spectra. Laser detuning experiments were used to show that the transition frequencies of J Å 9, 10, 11, 14, and 15 were below while J Å 12 and 13 were above the laser frequency of 890 760.2 MHz (8). The errors in the net Stark shift (rms deviations of the individual shifts), laser frequency (0.2 MHz), and experimental setup (0.5 MHz) were combined to yield the overall uncertainty in the zero-field frequency. The uncertainties in the Stark coefficients were not considered in the present error analysis. Despite these uncertainties, the 13CD3OD zero-field frequencies determined here should contribute significantly to the improvement of the electric dipole moment components and molecular constants because no other high-resolution far-infrared studies have been reported on this molecule. We observe several absorption lines belonging to additional Q-branch and P- (or R-) branch transitions which have not yet been assigned. More extensive spectra and analysis at other laser lines are being pursued and will be reported. Further analysis of the Q-branch multiplet will provide information on the series expansion coefficients.
ACKNOWLEDGMENT We are grateful to Dr. I. Mukhopadhyay of the Centre for Advanced Technology, Indore, India for providing the energy level predictions and Stark coefficients of 13CD3OD.
Copyright q 1996 by Academic Press, Inc.
AID
JMS 7008
/
6t0a$$$582
04-22-96 11:45:06
mspas
AP: Mol Spec
441
LETTER TO THE EDITOR
REFERENCES 1. L. H. Johnston, R. P. Srivastava, and R. M. Lees, J. Mol. Spectrosc. 84, 1–40 (1980). 2. R. L. Bhattacharjee, L. H. Johnston, G. R. Sudhakaran, and J. C. Sarker, J. Mol. Spectrosc. 138, 38–48 (1989). 3. L. H. Johnston, J. C. Sarker, R. L. Bhattacharjee, and G. R. Sudhakaran, J. Mol. Spectrosc. 123, 501–502 (1987). 4. J. C. Sarker, G. R. Sudhakaran, R. L. Bhattacharjee, L. H. Johnston,
5. 6. 7.
8.
I. Mukhopadhyay, and R. M. Lees, J. Mol. Spectrosc. 147, 243–251 (1991). G. R. Sudhakaran, M. Jackson, R. M. Lees, Li-Hong Xu, and I. Mukhopadhyay, Infrared Phys. 34, 661–665 (1993). I. Mukhopadhyay, private communication. I. Mukhopadhyay, P. K. Gupta, and G. R. Sudhakaran, in ‘‘International Conference on Spectroscopy: Frontiers and Perspectives, Bombay, India, 1996.’’ C. C. Bradley and D. J. E. Knight, Phys. Lett. A 32, 59–60 (1970).
Copyright q 1996 by Academic Press, Inc.
AID
JMS 7008
/
6t0a$$$582
04-22-96 11:45:06
mspas
AP: Mol Spec