Laser stark spectroscopy of CD3OD at 311 μm

JOURNAL OF MOLECULAR

SPECTROSCOPY

123, 501-502 (1987)

LETTER TO THE EDITOR Laser Stark Spectroscopy of CDBOD at 311 pm L. H. JOHNSTON, J. C. SARKER, R. L. BHATTACHARJEE,AND G. R. SUDHAKARAN Department of Physics, University of Idaho, Moscow, Idaho 83843

We report here the first observation of the Q-branch multiplet, J = 11to 18 members of the K = 1l + 10, E2, V, = 0 torsional state of fully deuterated methyl alcohol (CD,OD). Theseresonances havebeen observed between the3 1l-pm lineof the HCN laser and the Stark shifted frequency spectrum. The experimental procedure used in this work was described previously (I). Laser Stark spectra have been taken in both parallel and perpendicular polarization. Figure 1 shows the spectra up to 620 V with the Stark field parallel to the radiation electric field. The observed Stark voltages for different M-components are given in Table I. The Stark-plate spacing was 0.05 1508 f 0.00005 cm. This assignment is based on predictions of energy levels and Stark coefficients by R. M. Lees (2). The Stark energy shift, A W, of each level was calculated using the formula A W/h = (A + BM2)E2 - CME, where h is Plan&s constant, A, B, and C are the Starkcoefficients for a particular level, and E is the Stark electric field. The Stark frequency shift and the zero-field frequency of each member of the multiplet are given in Table II. Laser detuning experiments showed that the frequencies of J = 11, 12, and 13 are above and J = 14, 15, 16, 17, and 18 are below the laser frequency of 964 313.40 MHz (3). The probable error to the frequencies given in Table II is of the order of 1 MHz.

I

320

1

40

I

I

I

1

I

I

520

420

I

140

I 240

I VOLTS

I VOLTS

t

820

L

240

FIG. 1. Absorption of fully deuterated methyl alcohol (CD,OD)vapor versus Stark voltage in the parallel polarization, N = 0. Labeled features are JM components of the K = 11 + 10 E2 Q branch of the u, = 0 torsional state. 501

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502

LETTER TO THE EDITOR TABLE I

Observed Stark Voltages (in Volts) of Different M-Components in the Parallel Polarization (AAf = 0) for the JK = Ji, + & E2, o, = 0 Q-Branch Laser Stark Spectrum of CDsOD at 964 313.40 MHz

TABLE II Calculated Stark Shifts and the Zero-Field Frequencies for the Multiplet JK = J,, + Jlo Stark J

Shifts

zero-field

Frequencies

in MHZ

In MHZ

11

-414.90

964 728.30

12

-276.32

964 589.72

13

-123.40

964 436.80

14

44.16

964 269.24

15

225.29

964 088.11

16

422.12

963 891.28

17

634.21

963 679.19

18

862.28

963 461.12

We observe some absorption lines belonging to other transitions, which have not been assigned yet. More extensive spectra and analysis are being pursued and will be reported. These results provide information on the J-splittings of this Q branch and should contribute significantly to improved dipole moments and rotational constants for CD,OD. ACKNOWLEDGMENT We are grateful to Professor R. M. Lees for providing the energy level predictions and the Stark coefficients of CD,OD. RECEIVED:~C~~~W

23, 1986 REFERENCES

1. L. H. JOHNSTON,R. P. SRIVASTAVA, ANDR. M. LEES,J. Mol. Spectrosc., 84, l-40 (1980). 2. R. M. LEES,private communication.

3. L. 0. HOCKERANDA. JAVAN,Phys. Lett. A 25,489-490

(1967).